Explain the difference between ideal and non-ideal solutions with suitable examples.

📘 Ideal vs Non-Ideal Solutions

🔵 Step 1: Ideal Solution

An ideal solution is a solution that obeys Raoult's law over the entire range of composition and temperature.

P_i = x_iP_i°

In an ideal solution, the intermolecular attractions between A–A, B–B and A–B molecules are nearly equal.

ΔH_mix = 0

ΔV_mix = 0

Examples: Benzene + Toluene, n-Hexane + n-Heptane.

🟠 Step 2: Non-Ideal Solution

A non-ideal solution does not obey Raoult's law over the entire range of composition.

This occurs when the A–B intermolecular attractions are significantly different from A–A and B–B attractions.

Examples: Ethanol + Acetone, Chloroform + Acetone.

🟣 Step 3: Positive Deviation

When A–B attractions are weaker than A–A and B–B attractions, molecules escape more easily into the vapour phase.

Vapour pressure observed > Vapour pressure predicted by Raoult's law

This is called positive deviation.

Example: Ethanol + Acetone.

🔴 Step 4: Negative Deviation

When A–B attractions are stronger than A–A and B–B attractions, molecules escape less easily into the vapour phase.

Vapour pressure observed < Vapour pressure predicted by Raoult's law

This is called negative deviation.

Example: Chloroform + Acetone.

🎬 3D-Style Molecular Animation

Ideal solution: A–B attraction is approximately equal to A–A and B–B.

A B A B A B

📊 Step 5: Main Differences

Property	Ideal Solution	Non-Ideal Solution
Raoult's Law	Obeys completely	Shows deviation
A–B Interaction	Approximately equal to A–A and B–B	Different from A–A and B–B
ΔHmix	Zero	Non-zero
ΔVmix	Zero	Usually non-zero
Examples	Benzene + Toluene	Ethanol + Acetone

✅ Exam Summary

Ideal Solution → Raoult's Law obeyed

Non-Ideal Solution → Positive or Negative deviation

Positive deviation: A–B attraction weaker → higher vapour pressure.

Negative deviation: A–B attraction stronger → lower vapour pressure.

CBSE Class 10 Social Science (087) Sample Paper 1 - 2026-27

www.careerinformationportal.in

APNA CAREER PORTAL

www.careerinformationportal.in

CBSE Sample Practice Paper — 1  (High-Level / HOTS Edition, Session 2026–27)

Class: X (10th)

Subject: Social Science — Code: 087

Time: 3 Hours

Max. Marks: 80

Student Name: ______________________

Roll No.: __________

Section: __________

General Instructions:

1. This question paper is divided into five sections — A, B, C, D and E.

2. Section A has 20 objective-type questions (including 2 Assertion–Reasoning questions) carrying 1 mark each.

3. Section B has 6 Short Answer questions carrying 3 marks each.

4. Section C has 4 Long Answer questions carrying 5 marks each.

5. Section D has 3 Source/Case-based questions carrying 4 marks each, with internal sub-parts.

6. Section E has 2 Map-based questions carrying 5 marks each (one from History, one from Geography).

7. Internal choices have been provided in approximately one-third of the questions; attempt only one option wherever a choice is given.

8. This is a High-Level / HOTS practice edition — questions emphasise analysis, evaluation, and application of concepts across History, Geography, Political Science and Economics, rather than direct recall.

SECTION A  (1 Mark each) — Q1 to Q20

Questions are drawn from across History, Geography, Political Science and Economics.

Q1. The Non-Cooperation Movement was withdrawn after the Chauri Chaura incident mainly because: 1

(A) Gandhi lost popular support(B) Gandhi believed in non-violence as a core principle, not merely a strategy(C) the government suppressed the movement completely(D) the Congress was banned

Q2. Which of the following best explains why the Rowlatt Act triggered widespread protest across India? 1

(A) It reduced taxes(B) It curtailed civil liberties and allowed detention without trial(C) It promoted Indian industries(D) It introduced separate electorates

Q3. The Civil Disobedience Movement differed from the Non-Cooperation Movement primarily because: 1

(A) It involved only boycott of foreign goods(B) It included direct violation of colonial laws, such as the Salt Law(C) It was launched by Subhas Chandra Bose(D) It had no mass participation

Q4. Which statement best explains the link between print culture and the growth of nationalism in colonial India? 1

(A) Print played no role in the freedom struggle(B) Print media spread nationalist ideas rapidly, creating a shared political consciousness(C) Print was completely banned under colonial rule(D) Print served only religious purposes

Q5. Why did Gandhi's idea of Satyagraha rely on the power of truth rather than physical force? 1

(A) He lacked resources for armed struggle(B) He believed truth and non-violence carried a moral power capable of uniting people across differences(C) It was a less risky option(D) The British demanded it

Q6. Which factor best explains why the black (regur) soils of the Deccan Plateau are especially suited to cotton cultivation? 1

(A) High annual rainfall(B) The soil retains moisture well, meeting cotton's need for consistent water availability(C) Sandy texture of the soil(D) Presence of coal deposits nearby

Q7. Why has Kerala's sex ratio remained consistently favourable to women compared to most other Indian states? 1

(A) Its coastal climate(B) High female literacy, healthcare access and social awareness(C) Its low population density(D) Its coastal location

Q8. Why is groundwater over-exploitation a growing concern in India despite the country receiving adequate annual rainfall overall? 1

(A) Rainfall is evenly distributed throughout the year(B) Rainfall is concentrated in a few monsoon months, leading to over-reliance on groundwater in dry periods(C) Groundwater is an infinite resource(D) No regulatory policy exists on water use

Q9. Which of the following best explains the decline in India's competitive advantage in the jute industry in recent decades? 1

(A) Lack of raw jute production(B) Competition from synthetic substitutes and cheaper production in other countries(C) Government ban on jute products(D) Voluntary closure of all jute mills

Q10. Why are national highways often described as the "lifelines" of the Indian economy? 1

(A) They are the oldest roads in the country(B) They connect major cities and ports, facilitating trade, mobility and economic integration(C) They are entirely toll-free(D) They serve tourism purposes only

Q11. Beyond simply reducing conflict, which reasoning best explains why power-sharing is considered desirable in a democracy? 1

(A) It slows down decision-making(B) It upholds the spirit of democracy by accommodating diverse social groups and their interests(C) It weakens the government(D) It increases corruption

Q12. Belgium's community-based power-sharing arrangement was primarily designed to address which challenge? 1

(A) Economic inequality between regions(B) Regional and linguistic diversity and tension between communities(C) Threat of foreign invasion(D) Trade disputes with neighbours

Q13. Why is the "rule of law" considered a fundamental feature of good democratic government? 1

(A) It slows down the delivery of justice(B) It ensures no one, including those in power, is above the law, protecting citizens' rights(C) It always favours the majority community(D) It has only symbolic value

Q14. Which of the following best illustrates a challenge federalism can face when a single party dominates both central and state governments? 1

(A) Federalism is automatically strengthened(B) Power may become centralised in practice, reducing the autonomy states are meant to have(C) It has no real effect on governance(D) Centre-state cooperation always improves

Q15. Why do political parties often face internal challenges related to dynastic succession? 1

(A) Elections at the national level are rigged(B) Lack of internal democracy allows leadership positions to pass within families rather than through open competition(C) Parties generally dislike young leaders(D) Courts mandate such succession

Q16. Why might a country with a higher per capita income still rank lower on the Human Development Index (HDI) than a country with lower per capita income? 1

(A) HDI does not consider income at all(B) HDI also factors in health and education outcomes, which may be poorer despite higher income(C) HDI rankings are assigned randomly(D) Income has no relationship with development

Q17. Which best explains why the tertiary sector contributes the largest share to India's GDP despite employing a smaller share of the workforce than agriculture? 1

(A) Tertiary sector jobs are mostly seasonal(B) The tertiary sector includes high-value services with greater output/productivity per worker(C) Agriculture has completely stopped growing(D) The service sector employs the entire Indian workforce

Q18. Why does the Reserve Bank of India regulate the loans and interest rates offered by commercial banks? 1

(A) To reduce bank profits only(B) To ensure adequate credit flow to different sectors of the economy and protect economic stability(C) To influence the outcome of elections(D) To reduce the total number of banks

Q19. Assertion (A): Self-Help Groups (SHGs) have helped many poor people, especially women, overcome the problem of lack of collateral for loans.
Reason (R): SHG members pool their regular savings, and this collective saving acts as a substitute for collateral when the group approaches a bank for a loan. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Q20. Assertion (A): Globalisation has benefited all workers in India equally.
Reason (R): Globalisation has had a mixed impact — benefiting some groups, such as skilled workers and consumers who gain access to cheaper goods, while creating job insecurity for others, such as small producers competing with cheaper imports. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Page 1  |  www.careerinformationportal.in

www.careerinformationportal.in

SECTION B  (3 Marks each) — Q21 to Q26

Q21. "The Civil Disobedience Movement was different in nature from the Non-Cooperation Movement." Analyse this statement, supporting your answer with two examples. 3

Q22. Explain any three geographical factors responsible for the concentration of the iron and steel industry in the Chotanagpur plateau region. 3

— OR —

Analyse any three reasons why road transport is generally preferred over rail transport for short-distance movement of goods and people in India. 3

Q23. "Coalition governments can make power-sharing more effective in a democracy." Justify this statement with suitable examples. 3

Q24. Distinguish between horizontal and vertical distribution of power, giving one example of each from the Indian political system. 3

— OR —

Analyse why political parties are considered essential for the functioning of a democracy, even though people often criticise them. 3

Q25. "Money acts as an intermediate in the exchange process, making trade easier than the barter system." Explain this statement with a suitable example. 3

Q26. Examine any three ways in which consumer awareness and consumer rights protect the interests of buyers in the Indian market. 3

SECTION C  (5 Marks each) — Q27 to Q30

Q27. "The First World War, the Khilafat issue, and the events of 1919–1922 together turned Non-Cooperation into a genuine mass movement." Analyse this statement with reference to the participation of different social groups — peasants, workers, business classes, and women. 5

— OR —

Evaluate the role of print culture in shaping nationalist consciousness during the colonial period in India, with suitable examples. 5

Q28. Assess the impact of the Green Revolution on Indian agriculture, considering both its benefits and the environmental and regional imbalances it created. 5

— OR —

Examine the major challenges faced by manufacturing industries in India, and suggest measures for their sustainable development. 5

Q29. "Power-sharing arrangements can reduce the possibility of conflict between social groups." Examine this statement with reference to any two forms of power-sharing you have studied. 5

— OR —

Evaluate the major factors that have contributed to the erosion of public trust in political parties in contemporary democracies, and suggest reforms to strengthen them. 5

Q30. Discuss the role of formal and informal sources of credit in India, comparing their advantages and limitations, and explain why expanding formal credit remains important for development. 5

— OR —

Analyse the impact of globalisation on Indian producers, workers and consumers, citing both positive and negative consequences. 5

Page 2  |  www.careerinformationportal.in

www.careerinformationportal.in

SECTION D — Source/Case-Based Questions  (4 Marks each) — Q31 to Q33

Q31. Read the following source and answer the questions that follow:4

In March 1930, Mahatma Gandhi, along with a group of followers, set out on a march of over 240 miles from Sabarmati to the coastal town of Dandi, where he broke the salt law by manufacturing salt from seawater. Gandhi deliberately chose salt as a symbol of protest because it was something used daily by every Indian, rich or poor, and the government's monopoly and tax on salt production was seen as a particularly unjust burden on the common people. The march attracted huge crowds along its route and marked the beginning of the Civil Disobedience Movement, drawing participation from peasants, women, and even some sections of the business community.

(i) Which law did the Dandi March directly challenge? (1)

(ii) Why did Gandhi specifically choose salt as the symbol for this act of protest? (1)

(iii) Analyse how the Dandi March succeeded in mobilising different sections of Indian society. (2)

Q32. Read the following source and answer the questions that follow:4

Many regions in India face acute water scarcity despite adequate average rainfall, largely due to the seasonal and uneven distribution of rain, over-extraction of groundwater for irrigation, and inadequate water management infrastructure. Traditional rainwater harvesting systems, once widely used across the country, have declined with the growth of large dam and canal-based irrigation systems. In recent years, many communities and local governments have begun reviving traditional water conservation methods, alongside promoting more efficient irrigation techniques, to address the growing water crisis sustainably.

(i) Name one traditional method of rainwater harvesting used in India. (1)

(ii) Why does India face water scarcity despite having adequate average annual rainfall? (1)

(iii) Analyse why reviving traditional water conservation methods, alongside modern techniques, is considered a more sustainable approach to managing water resources. (2)

Q33. Read the following source and answer the questions that follow:4

Economic development is no longer measured by income alone. The Human Development Index (HDI), used internationally to compare countries, takes into account life expectancy, educational attainment, and per capita income together. A country may have a relatively high per capita income yet perform poorly on health and education indicators, resulting in a lower overall HDI ranking than expected. This shows that economic growth alone does not guarantee an improvement in the overall well-being and capabilities of a country's population.

(i) Name the three components that together make up the Human Development Index. (1)

(ii) Why can a country with high per capita income still have a comparatively low HDI ranking? (1)

(iii) Explain why economic growth (rising income) alone is not considered sufficient to measure a country's development. (2)

SECTION E — Map-Based Questions  (5 Marks each) — Q34 to Q35

Note: In the actual examination, these questions are attempted on a printed outline map of India provided along with the question paper.

Q34. (History) On an outline political map of India: 5

(i) Mark and label the following three places associated with the Indian National Movement, with an appropriate symbol at each location: (a) Dandi, (b) Champaran, (c) Amritsar (Jallianwala Bagh). (3)

(ii) Two places, marked as A and B on the map, are associated with important sessions of the Indian National Congress. Identify and name these two places. (2)

Q35. (Geography) On an outline physical/economic map of India: 5

(i) Mark and label the following three locations with an appropriate symbol at each: (a) Bhilai (iron and steel plant), (b) Digboi (oil field), (c) Mumbai High (offshore oil field). (3)

(ii) Two regions, marked as A and B on the map, are known for cotton textile and jute textile industries respectively. Identify and name these two regions/states. (2)

--- End of Question Paper --- All the best! ---

Page 3  |  www.careerinformationportal.in

www.careerinformationportal.in

APNA CAREER PORTAL

www.careerinformationportal.in

Design of Question Paper — Blueprint & Analysis

1. Section-wise Blueprint

Section	Question Type	No. of Questions	Marks each	Total Marks
A	Objective (MCQ incl. 2 Assertion–Reason)	20	1	20
B	Short Answer	6	3	18
C	Long Answer	4	5	20
D	Source/Case-Based (1+1+2)	3	4	12
E	Map-Based (History + Geography)	2	5	10
Total				80

2. Subject-wise (Discipline-wise) Marks Distribution

Discipline	Sec A	Sec B	Sec C	Sec D	Sec E	Total
History	5	3	5	4	5	22
Geography	5	3	5	4	5	22
Political Science	5	6	5	0	0	16
Economics	5	6	5	4	0	20
Total	20	18	20	12	10	80

3. Competency-Level Distribution — High-Level / HOTS Edition

Competency Level	Description	Marks	Percentage
Remembering & Understanding	Recall of facts, definitions, direct concept-based questions	24	30%
Applying	Application of concepts to explain, justify, or illustrate situations	26	32.5%
Analysing, Evaluating & Creating (HOTS)	Analysis, comparison, evaluation, and source/case-based reasoning across disciplines	30	37.5%
Total		80	100%

Note: This edition weights more marks toward analytical and evaluative (HOTS) questions than a standard-difficulty paper, to build stronger practice for board-level "analyse", "examine", and "assess"-type questions.

4. Internal Choice Summary

Internal choices are provided in Q22, Q24, Q27, Q28, Q29 and Q30 — approximately one-third of the total questions in Sections B and C.

Page 4 (Blueprint & Analysis)  |  www.careerinformationportal.in

www.careerinformationportal.in

Answer Key

Section A — Answer Key (1 mark each)

Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	(B)	6	(B)	11	(B)	16	(B)
2	(B)	7	(B)	12	(B)	17	(B)
3	(B)	8	(B)	13	(B)	18	(B)
4	(B)	9	(B)	14	(B)	19	(A)
5	(B)	10	(B)	15	(B)	20	(D)

Section B — Key Points (3 marks each)

Q21. Civil Disobedience involved actively breaking colonial laws (e.g., the Salt Law), unlike Non-Cooperation, which involved withdrawal/boycott without direct law-breaking; e.g., illegal salt manufacture, and refusal to pay taxes in some regions.

Q22. Proximity to iron ore, coal and manganese deposits; availability of cheap labour; good transport and market connectivity via railways (any three).

OR: Roads are cheaper to construct, can navigate difficult terrain, provide door-to-door connectivity, and are more economical for short distances than the fixed infrastructure of railways.

Q23. Coalition governments require different parties to negotiate and share power, ensuring wider representation of diverse interests; e.g., regional parties gaining a voice in national coalition governments in India.

Q24. Horizontal distribution: power shared among different organs of government at the same level (e.g., legislature, executive, judiciary); Vertical distribution: power shared among different levels of government (e.g., Union, State, and local/Panchayati Raj governments in India).

OR: Political parties structure electoral choices, form and run governments, and provide a mechanism for people's demands to be represented and translated into policy, despite their imperfections.

Q25. Money removes the need for a "double coincidence of wants" required in barter; e.g., a farmer can sell wheat for money and use that money to buy any other good or service, unlike in barter where both parties must want what the other offers.

Q26. Consumer awareness helps people demand fair pricing, quality standards, and accurate information; consumer courts/forums provide legal redressal against unfair trade practices; rights like the right to safety and right to information protect buyers from exploitation (any three).

Section C — Key Points (5 marks each)

Q27. WWI increased economic hardship (inflation, forced recruitment); the Khilafat issue united Hindus and Muslims in a common cause; peasants, workers and business classes each joined for distinct reasons (land revenue relief, wage/working condition demands, and protection from foreign competition respectively); women participated in large numbers, breaking social norms.

OR: Print media disseminated nationalist ideas, vernacular newspapers/pamphlets reached wider audiences, and iconography/print images built a shared sense of national identity; example: works of writers and nationalist newspapers spreading anti-colonial sentiment.

Q28. Benefits: increased foodgrain production, especially wheat, achieving self-sufficiency; drawbacks: regional imbalance (concentrated in Punjab, Haryana, western UP), overuse of groundwater and chemical inputs causing environmental degradation, and limited benefit to small farmers in other regions.

OR: Challenges: lack of infrastructure, high cost of credit, obsolete technology, competition from imports; measures: investment in infrastructure, skill development, promotion of cleaner production technologies, and support for small-scale industries.

Q29. Power-sharing among social groups (community-based, e.g. Belgium) and between different levels of government (vertical, e.g. Indian federalism) both accommodate diverse interests, reducing the likelihood that any single group feels excluded and resorts to conflict.

OR: Factors: dynastic politics, lack of internal democracy, growing role of money and muscle power in elections, unclear ideological differences; reforms: legal regulation of party funding, mandatory internal elections, stricter criminal-record disclosure norms.

Q30. Formal sources (banks, cooperatives) offer regulated interest rates and legal protection but are less accessible to the poor; informal sources (moneylenders, traders) are more accessible but often charge exploitative interest rates; expanding formal credit access, especially through means like SHGs, helps protect borrowers and supports development.

OR: Producers face increased competition from imports and MNCs (positive: better technology/quality; negative: pressure on small producers); workers face job insecurity in some sectors but new opportunities in others (e.g., IT/BPO); consumers benefit from wider choice and often lower prices.

Section D — Key Points (4 marks each)

Q31. (i) The Salt Law (British monopoly and tax on salt production). (ii) Salt was used daily by every Indian regardless of class, making the tax a universally felt and easily understood symbol of colonial injustice. (iii) The march passed through many villages, drawing growing crowds and support from peasants; it inspired parallel acts of civil disobedience across India; women and business groups also joined, broadening the movement's social base beyond its starting point.

Q32. (i) Examples include step-wells (baolis), tanks, or check dams (any correct traditional method). (ii) Because rainfall is highly seasonal and unevenly distributed across regions, leading to acute shortages outside the monsoon months and in low-rainfall areas. (iii) Traditional methods are low-cost, use local knowledge suited to specific terrain, and reduce over-dependence on groundwater/large dams, making water use more sustainable when combined with modern efficient irrigation techniques.

Q33. (i) Life expectancy (health), educational attainment (education), and per capita income. (ii) Because HDI also reflects health and education outcomes, and a country may under-invest in these even while its income levels are comparatively high. (iii) Because rising income alone does not guarantee improvements in people's health, education, or overall quality of life/capabilities, all of which are essential aspects of genuine development.

Section E — Key Points (5 marks each)

Q34. (i) Dandi (Gujarat coast), Champaran (Bihar), Amritsar/Jallianwala Bagh (Punjab) — to be marked with appropriate symbols. (ii) Locations to be identified based on the actual map provided (typically Lahore and Karachi, or other INC session venues as marked).

Q35. (i) Bhilai (Chhattisgarh), Digboi (Assam), Mumbai High (offshore, Arabian Sea) — to be marked with appropriate symbols. (ii) Cotton textile region — typically Maharashtra/Gujarat; Jute textile region — typically West Bengal, based on the actual map markings.

Page 5 (Answer Key)  |  www.careerinformationportal.in

www.careerinformationportal.in

Detailed Marking Scheme

General Marking Guidelines

• Section A (MCQ/Assertion-Reason): 1 mark for the correct option only; no partial credit.

• Section B (3-mark questions): marks distributed as 1 mark per valid point/example, up to a maximum of 3, or as per the reasoning-quality of the analysis provided.

• Section C (5-mark questions): marks awarded for depth of analysis, use of relevant examples/evidence, and a well-structured, logically consistent argument; full marks require addressing multiple dimensions of the question (e.g., both benefits and drawbacks, or multiple social groups/factors).

• Section D (Case-based, 4 marks): each sub-part is marked independently as indicated (1, 1, 2); the 2-mark sub-part requires both a valid point and a clear explanation/justification.

• Section E (Map-based, 5 marks each): 1 mark for each correctly located and labelled item (up to 3 marks), and 1 mark each for correctly identified/named locations in the second sub-part (up to 2 marks); marks are awarded only for locations marked within a reasonable/acceptable area on the map.

• For HOTS-based analytical questions, credit should be given generously for well-reasoned answers that differ from the model answer but demonstrate sound understanding and logical consistency.

Section-wise Mark Allocation Recap

Section	Marks
A — Objective (MCQ + Assertion-Reason)	20
B — Short Answer	18
C — Long Answer	20
D — Source/Case-Based	12
E — Map-Based	10
Total	80

This High-Level / HOTS sample paper, blueprint, and answer key are prepared for CBSE Class X Social Science (087) practice, Session 2026-27, in line with the current CBSE Question Paper Design and Competency-Based Education guidelines.

Page 6 (Marking Scheme)  |  www.careerinformationportal.in

CBSE Class 10 Science Sample Paper 10 - 2026-27

www.careerinformationportal.in

APNA CAREER PORTAL

www.careerinformationportal.in

CBSE Sample Practice Paper — 10  (Session 2026–27)

Class: X (10th)

Subject: Science — Code: 086

Time: 3 Hours

Max. Marks: 80

Student Name: ______________________

Roll No.: __________

Section: __________

General Instructions:

1. This question paper is divided into three parts — Part A (Chemistry, 25 Marks), Part B (Biology, 30 Marks) and Part C (Physics, 25 Marks).

2. Each part is further divided into four sections: Section 1 — Very Short Answer (including objective-type and Assertion–Reason questions), Section 2 — Short Answer, Section 3 — Long Answer, and Section 4 — Case/Source-based integrated question.

3. Internal choices have been provided in approximately one-third of the questions across the paper. Attempt only one option where a choice is given.

4. Draw neat, labelled diagrams wherever necessary.

5. Write balanced chemical equations wherever applicable.

6. Marks for each question are indicated against it.

PART A — CHEMISTRY  (25 Marks)

Section 1 — Very Short Answer  (1 Mark each) — Q1 to Q8

Q1. Name the type of reaction in which a more reactive element takes the place of a less reactive element in a compound. 1

Q2. Write the chemical formula of caustic soda. 1

Q3. State the colour change observed when a few drops of phenolphthalein are added to a basic solution. 1

Q4. Name the functional group present in aldehydes. 1

Q5. Identify the substance that gets oxidised in the reaction: ZnO + C → Zn + CO. 1

Q6. Write the common name and chemical formula of washing soda. 1

Q7. Assertion (A): Copper vessels develop a green coating when exposed to moist air for a long time.
Reason (R): Copper reacts slowly with moisture, carbon dioxide, and oxygen present in air to form a green basic copper carbonate layer on its surface. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Q8. Assertion (A): Diamond does not conduct electricity, while graphite does.
Reason (R): In diamond, each carbon atom is bonded to four other carbon atoms with no free electrons, whereas in graphite, each carbon atom is bonded to only three others, leaving one free electron per atom. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Section 2 — Short Answer  (2 Marks each) — Q9 to Q12

Q9. Write a balanced chemical equation for the reaction of iron with steam. State the type of reaction involved. 2

Q10. What is meant by a "precipitation reaction"? Give one example with a balanced chemical equation. 2

Q11. State any two reasons why gold and platinum are used for making jewellery rather than more reactive metals. 2

— OR —

Explain, with reason, why the decomposition of silver chloride in sunlight is considered a photochemical reaction. 2

Q12. Draw the electron dot structure of ethyne (C₂H₂), and state the type of bond present between the two carbon atoms. 2

Section 3 — Long Answer  (5 Marks) — Q13

Q13. (a) Describe the process of obtaining metals of medium reactivity (like iron and zinc) from their oxides through reduction with carbon, with a suitable example. (3)
(b) Why must metal ores be first converted to oxides (through roasting or calcination) before reduction with carbon? (2) 5

— OR —

(a) Define homologous series. State any two characteristic features of a homologous series with reference to alkanes. (3)
(b) Why does the melting and boiling point of carbon compounds in a homologous series generally increase with increasing molecular mass? (2)

Section 4 — Case-based Question  (4 Marks) — Q14

Q14. Read the following passage and answer the questions that follow.4

Most metals occur in nature combined with other elements in the form of compounds called minerals, and a mineral from which a metal can be profitably extracted is called an ore. The method used to extract a metal from its ore depends largely on the metal's position in the reactivity series. Highly reactive metals require electrolytic reduction, moderately reactive metals are usually extracted by reduction with carbon, and the least reactive metals often occur in their free (native) state and require little or no chemical processing to obtain the pure metal.

14.1 Define the term "ore". (1)

14.2 Name one metal that is typically extracted by electrolytic reduction because of its high reactivity. (1)

14.3 Explain why the method of extraction of a metal depends on its position in the reactivity series. (2)

--- Continued on next page ---

Page 1 of 5  |  www.careerinformationportal.in

www.careerinformationportal.in

PART B — BIOLOGY  (30 Marks)

Section 1 — Very Short Answer  (1 Mark each) — Q15 to Q22

Q15. Name the hormone secreted by the thyroid gland, and state the mineral required for its synthesis. 1

Q16. Define "tropic movement" in plants. 1

Q17. Name the process by which pollen grains are transferred from the anther to the stigma of a flower. 1

Q18. What is the term used for the physical and chemical features that are transmitted from parents to offspring? 1

Q19. In pea plants, a cross between a plant with round, yellow seeds (RrYy) and a plant with wrinkled, green seeds (rryy) is called a: 1

Q20. Name one ozone-depleting substance commonly released from refrigerators and air-conditioners. 1

Q21. Assertion (A): Phloem tissue can transport food materials both upward and downward in a plant.
Reason (R): Unlike xylem, phloem transport of food (translocation) occurs using energy from ATP, and can move materials in the direction required by different parts of the plant. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Q22. Assertion (A): A person who has undergone vasectomy can no longer produce sperm.
Reason (R): Vasectomy involves cutting and sealing the vas deferens, which blocks the passage of sperm from the testes but does not stop sperm production itself. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Section 2 — Short Answer  (2 Marks each) — Q23 to Q26

Q23. Name the hormone responsible for regulating the level of calcium and phosphate in the blood, and name the gland that secretes it. 2

Q24. Differentiate between spore formation in Rhizopus (bread mould) and budding in Hydra as modes of asexual reproduction. 2

— OR —

Explain why a large number of sperms are produced by a healthy human male, even though only one is needed for fertilisation. 2

Q25. What is the role of the gastric glands present in the stomach lining during digestion? 2

Q26. Name any two sexually transmitted infections, and state one way of preventing their spread. 2

Section 3 — Long Answer  (5 Marks each) — Q27 to Q28

Q27. (a) With reference to the human respiratory system, describe the pathway of air from the nostrils to the alveoli, naming each structure in sequence. (3)
(b) Why are alveoli well-suited for efficient exchange of gases? (2) 5

— OR —

(a) Describe the structure of the human excretory system, explaining the roles of the kidney, ureter, urinary bladder and urethra. (3)
(b) What is the role of ADH (antidiuretic hormone) in regulating the water content of urine? (2)

Q28. (a) Explain how a cross between a pure-breeding round-seeded (RR) pea plant and a pure-breeding wrinkled-seeded (rr) pea plant results in an entirely round-seeded F1 generation. What does this tell us about dominance? (3)
(b) If the F1 plants are self-pollinated, predict the phenotypic ratio expected in the F2 generation. (2) 5

— OR —

(a) Describe the mechanism of coordination between the nervous system and the endocrine system, using the example of the body's response to a sudden fright. (3)
(b) Why is hormonal (chemical) coordination generally slower but longer-lasting compared to nervous coordination? (2)

Section 4 — Case-based Question  (4 Marks) — Q29

Q29. Read the following passage and answer the questions that follow.4

A stable ecosystem depends on a balanced flow of energy and nutrients between its living and non-living components. Producers, such as green plants, capture solar energy and convert it into chemical energy, which is then passed on to various consumers through food chains. Decomposers, including bacteria and fungi, play an equally important role by breaking down the remains of dead organisms and waste products, releasing nutrients back into the soil so that they can be reused by producers, thereby completing the natural nutrient cycle.

29.1 Name the group of organisms that capture solar energy and convert it into chemical energy. (1)

29.2 What would happen to the nutrient cycle if decomposers were absent from an ecosystem? (1)

29.3 Explain, with an example, how decomposers help maintain the fertility of soil. (2)

--- Continued on next page ---

Page 2 of 5  |  www.careerinformationportal.in

www.careerinformationportal.in

PART C — PHYSICS  (25 Marks)

Section 1 — Very Short Answer  (1 Mark each) — Q30 to Q37

Q30. Define the "principal focus" of a concave mirror. 1

Q31. Name the phenomenon responsible for the sun being visible for a short while even after it has actually set below the horizon. 1

Q32. State one cause of presbyopia. 1

Q33. Write the formula relating electric power, resistance, and current. 1

Q34. Calculate the potential difference required to pass a current of 2 A through a resistor of 5 Ω. 1

Q35. Name the device used to detect the presence of a small current in a circuit, based on the deflection of a magnetic needle. 1

Q36. Assertion (A): A convex mirror always forms a virtual, erect and diminished image of an object, regardless of the object's distance from the mirror.
Reason (R): A convex mirror is a diverging mirror, so the reflected rays always appear to meet behind the mirror, no matter where the object is placed. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Q37. Assertion (A): Electrical appliances with a metallic body are always earthed.
Reason (R): Earthing provides a low-resistance path for leakage current to flow safely into the ground, protecting the user from electric shock in case of a fault. 1

(A) Both A and R are true, and R is the correct explanation of A. (B) Both A and R are true, but R is NOT the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.

Section 2 — Short Answer  (2 Marks each) — Q38 to Q41

Q38. Define "refractive index" of a medium with respect to air. 2

Q39. Why do we see a spectrum of colours when white light passes through a glass prism? 2

— OR —

An object is placed at the focus of a convex lens. State the nature and position of the image formed. 2

Q40. Calculate the electrical energy consumed by an appliance of power 1000 W used for 3 hours, expressing your answer in kilowatt-hours. 2

Q41. State any two factors on which the strength of the magnetic field produced at the centre of a current-carrying circular loop depends. 2

Section 3 — Long Answer  (5 Marks) — Q42

Q42. (a) With a labelled ray diagram, explain the formation of the image of an object placed between the pole and the focus of a concave mirror. (3)
(b) An object is placed 15 cm from a convex mirror of focal length 10 cm. Using the mirror formula, find the position of the image formed. (2) 5

— OR —

(a) With the help of a circuit diagram, explain how you would experimentally verify Ohm's law in a laboratory. (3)
(b) A wire of resistance 6 Ω is bent in the form of a circle. Calculate the effective resistance between two points diametrically opposite to each other on the circle. (2)

Section 4 — Case-based Question  (4 Marks) — Q43

Q43. Read the following passage and answer the questions that follow.4

Every current-carrying conductor is surrounded by a magnetic field, whose strength and pattern depend on the shape of the conductor and the amount of current flowing through it. This basic relationship between electricity and magnetism, discovered by Hans Christian Oersted, forms the basis for a wide range of devices that use magnetic fields produced by electric currents, from simple electromagnets used to sort scrap metal, to more complex instruments used in hospitals and industries.

43.1 Who discovered that a current-carrying conductor produces a magnetic field around it? (1)

43.2 Name one everyday device (other than a motor or generator) that makes use of an electromagnet. (1)

43.3 State two factors on which the strength of the magnetic field produced by a straight current-carrying conductor depends. (2)

--- End of Question Paper --- All the best! ---

Page 3 of 5  |  www.careerinformationportal.in

www.careerinformationportal.in

APNA CAREER PORTAL

www.careerinformationportal.in

Design of Question Paper — Blueprint & Competency Analysis

1. Part-wise & Section-wise Blueprint

Part	Section 1 (VSA + AR)	Section 2 (SA)	Section 3 (LA)	Section 4 (Case-based)	Total
A — Chemistry	8 × 1 = 8	4 × 2 = 8	1 × 5 = 5	1 × 4 = 4	25
B — Biology	8 × 1 = 8	4 × 2 = 8	2 × 5 = 10	1 × 4 = 4	30
C — Physics	8 × 1 = 8	4 × 2 = 8	1 × 5 = 5	1 × 4 = 4	25
Total	24	24	20	12	80

2. Unit-wise Weightage (as per given specification)

Unit	Topic Focus	Marks
Unit I — Chemical Substances	Chemical reactions/equations, acids/bases/salts, metals & non-metals, carbon compounds	25
Unit II — World of Living	Life processes, control & coordination, reproduction, heredity	25
Unit V — Natural Resources	Ecosystems, energy flow, decomposers, environmental issues	5
Unit III — Natural Phenomena	Reflection/refraction, human eye and its defects	12
Unit IV — Effects of Current	Ohm's law, resistance, magnetic effects (excluding motor/generator/EMI)	13
Total		80

3. Competency-Level Distribution

Competency Level	Approx. Marks	Approx. %
Knowledge & Understanding (state, define, list, describe, identify)	40	50%
Application (calculate, illustrate, show, explain, distinguish)	24	30%
Analyse, Evaluate & Create (interpret, analyse, compare, contrast, examine)	16	20%
Total	80	100%

4. Internal Choice Summary

Part A: Internal choice provided in Q11 (SA) and Q13 (LA) — 2 of 5 non-VSA questions (~40%).

Part B: Internal choice provided in Q24 (SA), Q27 (LA) and Q28 (LA) — 3 of 6 non-VSA questions (50%).

Part C: Internal choice provided in Q39 (SA) and Q42 (LA) — 2 of 5 non-VSA questions (~40%).

Overall, internal choices are provided in roughly one-third to one-half of the non-VSA questions across the paper, consistent with the CBSE 2026-27 design intent.

5. Exclusions Confirmed

✔ No questions from Periodic Classification of Elements.

✔ No questions from Evolution (speciation, fossils) — only Heredity concepts included.

✔ No questions on Electric Motor, Electromagnetic Induction, or Electric Generator.

✔ No content drawn from "Do You Know" / informational boxes in NCERT textbooks.

Page 4 of 5 (Blueprint & Analysis)  |  www.careerinformationportal.in

www.careerinformationportal.in

Answer Key & Marking Scheme (Key Points)

PART A — CHEMISTRY

Q1. Displacement reaction.

Q2. NaOH.

Q3. Colourless solution turns pink.

Q4. –CHO.

Q5. Carbon (C) gets oxidised to CO.

Q6. Washing soda; Na₂CO₃·10H₂O.

Q7. (A)   Q8. (A)

Q9. 3Fe + 4H₂O → Fe₃O₄ + 4H₂; a combination-type redox reaction (iron is oxidised, steam provides oxidising conditions).

Q10. A reaction in which an insoluble solid (precipitate) is formed when two solutions are mixed; e.g., BaCl₂ + Na₂SO₄ → BaSO₄↓ + 2NaCl.

Q11. Gold and platinum are highly unreactive, so jewellery made from them does not tarnish or corrode; they are also lustrous and malleable, making them suitable for intricate designs (any two points). OR: The decomposition of silver chloride occurs specifically due to exposure to light (sunlight), not heat; reactions that occur due to the absorption of light energy are called photochemical reactions.

Q12. Structure showing a C≡C triple bond, with each carbon also bonded to one hydrogen atom (HC≡CH); a triple covalent bond is present between the two carbon atoms.

Q13. (a) Metal oxides of medium-reactivity metals are reduced by heating with carbon, which is more reactive than the metal and takes away the oxygen; e.g., ZnO + C → Zn + CO. (b) Ores usually occur as sulphides or carbonates, not oxides; roasting (heating sulphide ores in air) or calcination (heating carbonate ores in limited air) converts them into oxides, which can then be more easily reduced by carbon. OR: A homologous series is a series of carbon compounds having the same general formula and similar chemical properties, where each successive member differs from the previous one by a –CH₂– unit; features: same general formula (e.g., CnH2n+2 for alkanes), same functional group, and gradual change in physical properties. (b) As molecular mass increases, the strength of intermolecular forces (van der Waals forces) between molecules increases, requiring more energy (higher temperature) to overcome them and change state.

Q14. (i) A mineral from which a metal can be extracted profitably and conveniently is called an ore. (ii) Sodium (or potassium/calcium/magnesium — any highly reactive metal). (iii) Since different metals require different amounts of energy to be separated from their compounds depending on their reactivity, highly reactive metals need strong methods like electrolysis, while less reactive metals can be extracted using simpler methods like heating with carbon or, for very unreactive metals, may not need any chemical extraction at all.

PART B — BIOLOGY

Q15. Thyroxine; iodine is required for its synthesis.

Q16. Tropic movement is the directional growth movement of a plant part in response to an external stimulus, either towards or away from it.

Q17. Pollination.

Q18. Heredity.

Q19. Test cross.

Q20. Chlorofluorocarbons (CFCs).

Q21. (A)   Q22. (D)

Q23. Parathyroid hormone (parathormone); secreted by the parathyroid gland.

Q24. In Rhizopus, tiny spores are formed inside sporangia and are released to develop into new individuals under favourable conditions; in Hydra, a new individual develops as a bud/outgrowth from the parent's body and eventually detaches to become independent. OR: A large number of sperms are produced to increase the probability that at least one sperm will successfully reach and fertilise the egg, since most sperms are lost or fail to reach the egg during their journey.

Q25. Gastric glands secrete gastric juice, containing hydrochloric acid (which kills bacteria and provides an acidic medium) and the enzyme pepsin (which digests proteins).

Q26. HIV-AIDS and gonorrhoea (any two valid examples); prevention — use of condoms during intercourse.

Q27. (a) Air passes through the nostrils → pharynx → larynx → trachea → bronchi → bronchioles → alveoli. (b) Alveoli have thin walls (one-cell thick), are richly supplied with blood capillaries, and provide a very large surface area, all of which allow efficient diffusion of oxygen and carbon dioxide. OR: Kidneys filter blood and form urine; ureters carry urine from kidneys to the urinary bladder; the bladder stores urine until it is expelled through the urethra. (b) ADH increases the reabsorption of water by the kidney tubules when the body needs to conserve water, resulting in the production of a smaller volume of more concentrated urine.

Q28. (a) Since F1 is entirely round-seeded, the round-seed trait (R) is dominant over the wrinkled-seed trait (r), which is recessive and remains hidden in the F1 generation. (b) On self-pollination of F1 (Rr × Rr), the F2 phenotypic ratio expected is 3 round : 1 wrinkled. OR: On sudden fright, the nervous system triggers an immediate reflex response (e.g., jumping back), while the adrenal gland simultaneously releases adrenaline into the blood, increasing heart rate and preparing the body for prolonged "fight or flight" action. (b) Hormones travel through the bloodstream to reach target organs, which takes more time than the electrical impulses of the nervous system, but their effects tend to last longer since hormone levels change and act gradually over time.

Q29. (i) Producers (green plants). (ii) Dead organic matter and waste would accumulate indefinitely, and essential nutrients would remain locked up, disrupting the cycling of nutrients and eventually limiting the growth of new producers. (iii) Decomposers break down dead plant and animal matter into simpler substances, releasing nutrients like nitrogen and phosphorus back into the soil, which are then absorbed by plant roots, enriching soil fertility (e.g., composting of dead leaves by fungi and bacteria).

PART C — PHYSICS

Q30. The principal focus of a concave mirror is the point on its principal axis where parallel rays of light, after reflection from the mirror, actually converge (meet).

Q31. Atmospheric refraction (advance sunrise/delayed sunset effect).

Q32. Gradual weakening of the ciliary muscles and reduced flexibility of the eye lens with age.

Q33. P = I²R.

Q34. V = IR = 2 × 5 = 10 V.

Q35. Galvanometer.

Q36. (A)   Q37. (A)

Q38. The refractive index of a medium with respect to air is the ratio of the speed of light in air (or vacuum) to the speed of light in that medium (n = c/v).

Q39. Different colours of white light have different wavelengths and are refracted by different amounts as they pass through the glass prism, causing them to separate and form a visible spectrum (dispersion). OR: The image formed is real, inverted, highly diminished, and formed at the focus on the other side of the convex lens... (correction: an object at the focus of a convex lens actually produces an image at infinity, highly enlarged; state accordingly) — the image forms at infinity and is real, inverted, and highly magnified.

Q40. Energy = P × t = 1000 W × 3 h = 3000 Wh = 3 kWh.

Q41. The number of turns in the coil, and the magnitude of current flowing through the coil (also depends on the radius of the loop).

Q42. (a) Diagram showing a virtual, erect, and magnified image formed behind the mirror when the object is between the pole and focus of a concave mirror. (b) For a convex mirror, f = +10 cm, u = −15 cm; using 1/v + 1/u = 1/f: 1/v = 1/10 − 1/(−15)... correctly, 1/v = 1/f − 1/u = 1/10 − 1/(−15) = 1/10 + 1/15 = 5/30 = 1/6 ⟹ v = 6 cm (behind the mirror, virtual image). OR: Standard Ohm's law verification circuit description using ammeter, voltmeter, rheostat, and battery, plotting V vs I to get a straight line confirming Ohm's law. (b) Bending the wire into a circle creates two equal semicircular arcs of 3 Ω each between the diametrically opposite points, connected in parallel: 1/R = 1/3+1/3 = 2/3 ⟹ R = 1.5 Ω.

Q43. (i) Hans Christian Oersted. (ii) Electric bell (or electromagnetic crane used to lift scrap iron). (iii) The magnitude of the current flowing through the conductor, and the distance from the conductor at which the field is measured.

Page 5 of 5 (Answer Key)  |  www.careerinformationportal.in

Some Basic Concepts of Chemistry

🧪 Some Basic Concepts of Chemistry

JEE Level — 6 Marks Questions — Tap a question to reveal full solution

🔵 Step 1: Moles of Each Gas

Moles CO₂ = 4.4 ÷ 44 = 0.1 mol

Moles O₂ = 3.2 ÷ 32 = 0.1 mol

Moles H₂ = 2.0 ÷ 2 = 1.0 mol

🟢 Step 2: Total Moles

Total moles = 0.1 + 0.1 + 1.0 = 1.2 mol

🟣 Step 3: Total Number of Molecules

1.2 × 6.022 × 10²³ = 7.226 × 10²³ molecules

🟠 Step 4: Mole Fraction of Each Gas

x(CO₂) = 0.1 ÷ 1.2 = 0.083

x(O₂) = 0.1 ÷ 1.2 = 0.083

x(H₂) = 1.0 ÷ 1.2 = 0.833

✅ Final Answer

Total molecules = 7.226 × 10²³

Mole fractions: CO₂ = 0.083, O₂ = 0.083, H₂ = 0.833

🔵 Step 1: Mass of Carbon (from CO₂)

Moles CO₂ = 0.88 ÷ 44 = 0.02 mol = moles C

Mass C = 0.02 × 12 = 0.24 g

🟢 Step 2: Mass of Hydrogen (from H₂O)

Moles H₂O = 0.36 ÷ 18 = 0.02 mol → moles H = 0.04 mol

Mass H = 0.04 × 1 = 0.04 g

🟣 Step 3: Mass of Oxygen (by difference)

Mass O = 0.44 − 0.24 − 0.04 = 0.16 g

Moles O = 0.16 ÷ 16 = 0.01 mol

🟠 Step 4: Mole Ratio

C : H : O = 0.02 : 0.04 : 0.01 = 2 : 4 : 1

✅ Final Answer

Empirical Formula = C₂H₄O

🔵 Step 1: Moles of Each Reactant

Moles Al = 5.4 ÷ 27 = 0.2 mol

Moles Cl₂ = 14.2 ÷ 71 = 0.2 mol

🟢 Step 2: Compare With Stoichiometric Ratio (2 : 3)

0.2 mol Al needs (3/2)×0.2 = 0.3 mol Cl₂

Only 0.2 mol Cl₂ available → Cl₂ is limiting

✅ Limiting Reagent = Cl₂

🟣 Step 3: Moles of AlCl₃ Formed

Using Cl₂: moles AlCl₃ = (2/3) × 0.2 = 0.1333 mol

🟠 Step 4: Mass of AlCl₃

Molar mass AlCl₃ = 27 + (3×35.5) = 133.5 g/mol

Mass = 0.1333 × 133.5 = 17.8 g

✅ Final Answer

Limiting Reagent = Cl₂

Mass of AlCl₃ formed = 17.8 g

🔵 Step 1: Reaction on Heating

Only NaHCO₃ decomposes on heating:

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

🟢 Step 2: Moles of CO₂ and NaHCO₃

Moles CO₂ = 0.56 ÷ 44 = 0.01273 mol

Moles NaHCO₃ = 2 × 0.01273 = 0.02545 mol

🟣 Step 3: Mass of NaHCO₃ and Na₂CO₃

Mass NaHCO₃ = 0.02545 × 84 = 2.138 g

Mass Na₂CO₃ = 2.50 − 2.138 = 0.362 g

🟠 Step 4: Percentage Composition

% NaHCO₃ = (2.138/2.50) × 100 = 85.5%

% Na₂CO₃ = 14.5%

✅ Final Answer

NaHCO₃ = 85.5%  |  Na₂CO₃ = 14.5%

🔵 Step 1: Set Up Equations

Let x = mass CaCO₃, y = mass MgCO₃; x + y = 10

CaCO₃ → CaO + CO₂ (loses 44/100 of mass)
MgCO₃ → MgO + CO₂ (loses 44/84 of mass)

🟢 Step 2: Mass Loss Equation

Total mass loss = 10.0 − 5.20 = 4.80 g

0.44x + 0.5238(10−x) = 4.80

🟣 Step 3: Solve for x and y

−0.0838x = −0.438 → x = 5.23 g CaCO₃

y = 10 − 5.23 = 4.77 g MgCO₃

✅ Final Answer

CaCO₃ = 52.3%  |  MgCO₃ = 47.7%

🔵 Step 1: Moles of KClO₃

Molar mass KClO₃ = 39+35.5+48 = 122.5 g/mol

Moles = 5.00 ÷ 122.5 = 0.0408 mol

🟢 Step 2: Moles of O₂ (ratio 2:3)

Moles O₂ = (3/2) × 0.0408 = 0.0612 mol

🟣 Step 3: Volume of O₂ at STP

Volume = 0.0612 × 22.4 = 1.371 L

🟠 Step 4: Number of O₂ Molecules

0.0612 × 6.022×10²³ = 3.687 × 10²² molecules

✅ Final Answer

Volume of O₂ = 1.371 L  |  Molecules = 3.687 × 10²²

🔵 Step 1: Mole Ratio from % Composition

C = 85.7 ÷ 12 = 7.14

H = 14.3 ÷ 1 = 14.3

Ratio C : H = 7.14 : 14.3 = 1 : 2

✅ Empirical Formula = CH₂

🟢 Step 2: Molar Mass from Vapour Density

Molar Mass = 2 × Vapour Density = 2 × 21 = 42 g/mol

🟣 Step 3: Find n

Empirical formula mass (CH₂) = 14

n = 42 ÷ 14 = 3

✅ Final Answer

Empirical Formula = CH₂

Molecular Formula = C₃H₆

🔵 Step 1: Total Moles of CO₂

Moles CO₂ = 1.12 ÷ 22.4 = 0.05 mol

🟢 Step 2: Set Up Equations

Let x = mol Na₂CO₃, y = mol NaHCO₃ (both give 1:1 CO₂)

x + y = 0.05

106x + 84y = 5.00

🟣 Step 3: Solve

106(0.05−y) + 84y = 5.00 → −22y = −0.30

y = 0.0136 mol (NaHCO₃), x = 0.0364 mol (Na₂CO₃)

🟠 Step 4: Convert to Mass

Mass Na₂CO₃ = 0.0364 × 106 = 3.86 g

Mass NaHCO₃ = 0.0136 × 84 = 1.14 g

✅ Final Answer

Na₂CO₃ = 3.86 g (77.1%)  |  NaHCO₃ = 1.14 g (22.9%)

🔵 Step 1: Moles of Each Reactant

Moles CaCO₃ = 10 ÷ 100 = 0.1 mol

Moles HCl = 0.100 L × 1.0 M = 0.1 mol

🟢 Step 2: Compare With Ratio (1:2)

0.1 mol CaCO₃ needs 0.2 mol HCl, only 0.1 mol available

✅ Limiting Reagent = HCl

🟣 Step 3: Moles of CO₂ Formed

Moles CO₂ = moles HCl ÷ 2 = 0.1 ÷ 2 = 0.05 mol

🟠 Step 4: Volume at STP

Volume = 0.05 × 22.4 = 1.12 L

✅ Final Answer

Limiting Reagent = HCl

Volume of CO₂ = 1.12 L

🔵 Step 1: Moles of NaCl

Molar mass NaCl = 58.5 g/mol

Moles = 5.85 ÷ 58.5 = 0.1 mol

🟢 Step 2: Molality

Molality = moles solute ÷ kg solvent = 0.1 ÷ 0.500 = 0.2 m

🟣 Step 3: Moles of Water

Moles H₂O = 500 ÷ 18 = 27.78 mol

🟠 Step 4: Mole Fraction of NaCl

x(NaCl) = 0.1 ÷ (0.1+27.78) = 3.59 × 10⁻³

✅ Final Answer

Molality = 0.2 m  |  Mole fraction of NaCl = 3.59 × 10⁻³

🔵 Step 1: Moles of CO₂

Moles CO₂ = 3.36 ÷ 22.4 = 0.15 mol

🟢 Step 2: Moles of CaCO₃ (1:1 ratio)

Moles CaCO₃ = 0.15 mol

🟣 Step 3: Mass of CaCO₃

Mass = 0.15 × 100 = 15 g

🟠 Step 4: Percentage

% CaCO₃ = (15 ÷ 20) × 100 = 75%

✅ Final Answer

Percentage of CaCO₃ = 75%

🔵 Step 1: Mole Ratio

C = 92.3 ÷ 12 = 7.69

H = 7.7 ÷ 1 = 7.7

Ratio C:H = 1:1

✅ Empirical Formula = CH

🟢 Step 2: Empirical Formula Mass

CH = 12 + 1 = 13 g/mol

🟣 Step 3: Find n

n = 78 ÷ 13 = 6

✅ Final Answer

Empirical Formula = CH

Molecular Formula = C₆H₆ (Benzene)

🔵 Step 1: Moles of Each Reactant

Moles H₂ = 2.0 ÷ 2 = 1.0 mol

Moles O₂ = 16 ÷ 32 = 0.5 mol

🟢 Step 2: Compare With Ratio (2:1)

1.0 mol H₂ needs exactly 0.5 mol O₂ — this exactly matches what is available!

✅ Reactants are in exact stoichiometric ratio — no limiting reagent, both fully consumed

🟣 Step 3: Mass of Water Formed

Moles H₂O = moles H₂ = 1.0 mol

Mass = 1.0 × 18 = 18 g

✅ Final Answer

No limiting reagent (exact stoichiometric mixture)

Mass of H₂O formed = 18 g

Excess reactant remaining = 0 g

🔵 Step 1: Reaction and Mass Loss

2NaHCO₃ → Na₂CO₃ + H₂O + CO₂

Mass loss = 10 − 6.90 = 3.10 g (as CO₂+H₂O)

🟢 Step 2: Moles of NaHCO₃

2 mol NaHCO₃ (168 g) loses 62 g (CO₂+H₂O)

Let n = mol NaHCO₃; loss = 31n = 3.10 → n = 0.1 mol

🟣 Step 3: Mass of NaHCO₃ and Na₂CO₃

Mass NaHCO₃ = 0.1 × 84 = 8.4 g

Mass Na₂CO₃ (original) = 10 − 8.4 = 1.6 g

🟠 Step 4: Verify Residue

Residue = 1.6 + (0.05 × 106) = 1.6 + 5.3 = 6.9 g ✓ matches given data

✅ Final Answer

NaHCO₃ = 84%  |  Na₂CO₃ = 16%

🔵 Step 1: Mass of Carbon and Hydrogen

Moles CO₂ = 4.4÷44 = 0.1 mol → mass C = 0.1×12 = 1.2 g

Moles H₂O = 1.8÷18 = 0.1 mol → moles H = 0.2 mol → mass H = 0.2 g

🟢 Step 2: Mass of Oxygen (by difference)

Mass O = 2.0 − 1.2 − 0.2 = 0.6 g → moles O = 0.6÷16 = 0.0375 mol

🟣 Step 3: Mole Ratio

C : H : O = 0.1 : 0.2 : 0.0375 = 8 : 16 : 3 (dividing by 0.0375, ×3)

⚠️ Note: this gives empirical formula mass ≈ 160 g/mol, which is already greater than the given molar mass of 60 g/mol. This means the numbers in the question are not mutually consistent (a real compound's molecular mass can never be smaller than its empirical formula mass). The method above is the correct approach — with consistent data you would proceed to find n = Molar Mass ÷ Empirical Formula Mass and multiply the empirical formula by n to get the molecular formula.

✅ Working Shown

% composition: C = 60%, H = 10%, O = 30% by mass

Empirical formula (as calculated) = C₈H₁₆O₃

Please double-check the given data (mass of sample / CO₂ / H₂O / molar mass) — as stated, it does not correspond to a valid molecular formula at M = 60 g/mol.