🧪 CLASS 10 SCIENCE
Chemical Reactions and Equations
रासायनिक अभिक्रियाएँ एवं समीकरण
Chemical Reactions and Equations
रासायनिक अभिक्रियाएँ एवं समीकरण
1️⃣ Description / परिचय
English
A chemical reaction is a process in which one or more substances change into new substances having different chemical properties. The substances which take part in a chemical reaction are called reactants, while the new substances formed are called products. A chemical equation represents a chemical reaction using symbols and chemical formulae. A complete chemical equation represents:
- Reactants
- Products
- Physical states
- Balanced number of atoms
- Reaction conditions, wherever required
हिन्दी
रासायनिक अभिक्रिया वह प्रक्रिया है जिसमें एक या एक से अधिक पदार्थ परिवर्तित होकर नए पदार्थ बनाते हैं जिनके रासायनिक गुण अलग होते हैं। अभिक्रिया में भाग लेने वाले पदार्थों को अभिकारक (Reactants) तथा बनने वाले नए पदार्थों को उत्पाद (Products) कहते हैं। रासायनिक समीकरण किसी रासायनिक अभिक्रिया को संकेतों तथा रासायनिक सूत्रों द्वारा प्रदर्शित करता है। एक पूर्ण रासायनिक समीकरण में निम्न जानकारी होती है:
- अभिकारक
- उत्पाद
- भौतिक अवस्थाएँ
- संतुलित परमाणु संख्या
- आवश्यक होने पर अभिक्रिया की परिस्थितियाँ
2️⃣ Animation / अभिक्रिया का Animation
Magnesium + Oxygen → Magnesium Oxide
मैग्नीशियम + ऑक्सीजन → मैग्नीशियम ऑक्साइड
मैग्नीशियम + ऑक्सीजन → मैग्नीशियम ऑक्साइड
Mg
O₂
MgO
→
→
Reactants → Reaction → Product
अभिकारक → अभिक्रिया → उत्पाद
अभिकारक → अभिक्रिया → उत्पाद
2Mg(s) + O₂(g) → 2MgO(s)
Animation Explanation / Animation की व्याख्या:
English: Magnesium reacts with oxygen and forms magnesium oxide.
हिन्दी: मैग्नीशियम ऑक्सीजन के साथ अभिक्रिया करके मैग्नीशियम ऑक्साइड बनाता है।
3️⃣ Physical States / भौतिक अवस्थाएँ
| Symbol | English | हिन्दी | Example |
|---|---|---|---|
| (s) | Solid | ठोस | Mg(s) |
| (l) | Liquid | द्रव | H₂O(l) |
| (g) | Gas | गैस | O₂(g) |
| (aq) | Aqueous solution | जलीय विलयन | HCl(aq) |
Board Tip / बोर्ड टिप:
यदि प्रश्न में physical state पूछी जाए तो (s), (l), (g), (aq) को जरूर लिखें।
यदि प्रश्न में physical state पूछी जाए तो (s), (l), (g), (aq) को जरूर लिखें।
4️⃣ Complete Chemical Equation / पूर्ण रासायनिक समीकरण
Zn(s) + 2HCl(aq)
→ ZnCl₂(aq) + H₂(g)
English: Zn and HCl are reactants. ZnCl₂ and H₂ are products. The symbols indicate their physical states.
हिन्दी: Zn और HCl अभिकारक हैं। ZnCl₂ और H₂ उत्पाद हैं। (s), (aq) तथा (g) उनकी भौतिक अवस्थाएँ बताते हैं।
5️⃣ Full Solved Examples / पूर्ण हल किए गए उदाहरण
Example 1 / उदाहरण 1:
Write and balance:
Mg + O₂ → MgO
Write and balance:
Mg + O₂ → MgO
Step 1:
Identify reactants.
Mg and O₂ are reactants.
चरण 1: Mg और O₂ अभिकारक हैं।
Step 2: Count atoms.
Left: Mg = 1, O = 2
Right: Mg = 1, O = 1
Step 3: Balance oxygen by putting 2 before MgO.
Step 4: Put 2 before Mg.
Mg and O₂ are reactants.
चरण 1: Mg और O₂ अभिकारक हैं।
Step 2: Count atoms.
Left: Mg = 1, O = 2
Right: Mg = 1, O = 1
Step 3: Balance oxygen by putting 2 before MgO.
Mg + O₂ → 2MgO
Now Mg becomes 2 on the right.
Step 4: Put 2 before Mg.
2Mg + O₂ → 2MgO
Final Answer:
2Mg(s) + O₂(g) → 2MgO(s)
Example 2 / उदाहरण 2:
Balance:
Fe + H₂O → Fe₃O₄ + H₂
Balance:
Fe + H₂O → Fe₃O₄ + H₂
Step 1:
Fe₃O₄ contains 3 Fe and 4 O atoms.
Step 2: Put 3 before Fe and 4 before H₂O.
Step 2: Put 3 before Fe and 4 before H₂O.
3Fe + 4H₂O → Fe₃O₄ + H₂
Step 3:
There are 8 H atoms on the left.
Therefore put 4 before H₂.
3Fe + 4H₂O → Fe₃O₄ + 4H₂
Final Answer:
3Fe(s) + 4H₂O(g)
→ Fe₃O₄(s) + 4H₂(g)
Example 3 / उदाहरण 3:
Zn + HCl → ZnCl₂ + H₂
Zn + HCl → ZnCl₂ + H₂
Step 1:
Zn is already balanced.
Step 2: ZnCl₂ contains 2 chlorine atoms. Therefore put 2 before HCl.
Final Answer:
Step 2: ZnCl₂ contains 2 chlorine atoms. Therefore put 2 before HCl.
Zn + 2HCl → ZnCl₂ + H₂
Step 3:
Hydrogen atoms = 2 on both sides.
Therefore equation is balanced.
Final Answer:
Zn(s) + 2HCl(aq)
→ ZnCl₂(aq) + H₂(g)
6️⃣ 50 CBSE Board Questions with Full Step-by-Step Solutions
Q1. What is a chemical reaction?
रासायनिक अभिक्रिया क्या है?
Step 1: Identify the process.
A chemical reaction is a process in which substances change.
Step 2: Understand the result.
New substances with different properties are formed.
Final Answer: A chemical reaction is a process in which one or more substances change into new substances having different chemical properties.
हिन्दी: रासायनिक अभिक्रिया वह प्रक्रिया है जिसमें एक या अधिक पदार्थ परिवर्तित होकर नए पदार्थ बनाते हैं जिनके गुण अलग होते हैं।
A chemical reaction is a process in which substances change.
Step 2: Understand the result.
New substances with different properties are formed.
Final Answer: A chemical reaction is a process in which one or more substances change into new substances having different chemical properties.
हिन्दी: रासायनिक अभिक्रिया वह प्रक्रिया है जिसमें एक या अधिक पदार्थ परिवर्तित होकर नए पदार्थ बनाते हैं जिनके गुण अलग होते हैं।
Q2. What are reactants and products?
अभिकारक और उत्पाद क्या हैं?
अभिकारक और उत्पाद क्या हैं?
Step 1:
Substances present before the reaction are called reactants.
अभिक्रिया से पहले उपस्थित पदार्थ अभिकारक कहलाते हैं।
Step 2: Substances formed after the reaction are called products.
अभिक्रिया के बाद बनने वाले पदार्थ उत्पाद कहलाते हैं।
Answer: Reactants → substances taking part in reaction.
Products → new substances formed.
अभिक्रिया से पहले उपस्थित पदार्थ अभिकारक कहलाते हैं।
Step 2: Substances formed after the reaction are called products.
अभिक्रिया के बाद बनने वाले पदार्थ उत्पाद कहलाते हैं।
Answer: Reactants → substances taking part in reaction.
Products → new substances formed.
Q3. What is a chemical equation?
रासायनिक समीकरण क्या है?
रासायनिक समीकरण क्या है?
A chemical equation represents a chemical reaction using symbols
and formulae.
रासायनिक समीकरण रासायनिक अभिक्रिया को संकेतों और रासायनिक सूत्रों द्वारा प्रदर्शित करता है।
Example:
रासायनिक समीकरण रासायनिक अभिक्रिया को संकेतों और रासायनिक सूत्रों द्वारा प्रदर्शित करता है।
Example:
2H₂ + O₂ → 2H₂O
Q4. Why should chemical equations be balanced?
रासायनिक समीकरण को संतुलित क्यों करना चाहिए?
रासायनिक समीकरण को संतुलित क्यों करना चाहिए?
Step 1:
According to the law of conservation of mass, matter cannot be
created or destroyed.
Step 2: Therefore the number of atoms of each element must be equal on both sides.
Final Answer: Chemical equations are balanced to obey the law of conservation of mass.
हिन्दी: द्रव्यमान संरक्षण के नियम के कारण समीकरण को संतुलित किया जाता है।
Step 2: Therefore the number of atoms of each element must be equal on both sides.
Final Answer: Chemical equations are balanced to obey the law of conservation of mass.
हिन्दी: द्रव्यमान संरक्षण के नियम के कारण समीकरण को संतुलित किया जाता है।
Q5. What is represented by (s), (l), (g) and (aq)?
(s) = Solid / ठोस
(l) = Liquid / द्रव
(g) = Gas / गैस
(aq) = Aqueous solution / जलीय विलयन
(l) = Liquid / द्रव
(g) = Gas / गैस
(aq) = Aqueous solution / जलीय विलयन
Q6. Balance H₂ + O₂ → H₂O.
Step 1:
O atoms = 2 on left and 1 on right.
Put 2 before H₂O.
H₂ + O₂ → 2H₂O
Step 2:
Now H atoms = 4 on right.
Put 2 before H₂.
2H₂ + O₂ → 2H₂O
Final Answer:
2H₂ + O₂ → 2H₂O
Q7. Balance Mg + O₂ → MgO.
O₂ has 2 oxygen atoms.
Put 2 before MgO.
Mg + O₂ → 2MgO
Now Mg = 2 on right. Put 2 before Mg.
Mg + O₂ → 2MgO
Now Mg = 2 on right. Put 2 before Mg.
2Mg + O₂ → 2MgO
Answer:
2Mg(s) + O₂(g) → 2MgO(s)
Q8. Write the equation for zinc with hydrochloric acid.
Reactants:
Zn + HCl
Products: ZnCl₂ + H₂
Cl atoms = 2 in ZnCl₂. Therefore put 2 before HCl.
Products: ZnCl₂ + H₂
Cl atoms = 2 in ZnCl₂. Therefore put 2 before HCl.
Zn + 2HCl → ZnCl₂ + H₂
With states:
Zn(s) + 2HCl(aq)
→ ZnCl₂(aq) + H₂(g)
Q9. What happens when magnesium burns in oxygen?
Magnesium combines with oxygen to form magnesium oxide.
हिन्दी: मैग्नीशियम ऑक्सीजन से अभिक्रिया करके मैग्नीशियम ऑक्साइड बनाता है।
2Mg + O₂ → 2MgO
This is a combination reaction.
It is also exothermic because heat and light are released.
हिन्दी: मैग्नीशियम ऑक्सीजन से अभिक्रिया करके मैग्नीशियम ऑक्साइड बनाता है।
Q10. Why is magnesium ribbon cleaned before burning?
Magnesium reacts slowly with oxygen in air and develops a thin layer
of magnesium oxide.
This layer prevents magnesium from coming directly in contact with oxygen.
Therefore the ribbon is cleaned to remove the oxide layer.
This layer prevents magnesium from coming directly in contact with oxygen.
Therefore the ribbon is cleaned to remove the oxide layer.
Q11. What is a combination reaction?
Two or more substances combine to form a single product.
Product = 1
Therefore it is a combination reaction.
CaO + H₂O → Ca(OH)₂
Reactants = 2
Product = 1
Therefore it is a combination reaction.
Q12. What is decomposition reaction?
A single compound breaks into two or more simpler substances.
CaCO₃ → CaO + CO₂
One reactant produces two products.
Therefore it is a decomposition reaction.
Q13. Give an example of thermal decomposition.
When calcium carbonate is heated:
CaCO₃(s) → CaO(s) + CO₂(g)
Heat causes decomposition.
Therefore it is thermal decomposition.
Q14. What is displacement reaction?
A more reactive element displaces a less reactive element from its
compound.
Fe + CuSO₄ → FeSO₄ + Cu
Iron is more reactive than copper, so iron displaces copper.
Q15. What is double displacement reaction?
Two compounds exchange their ions and form two new compounds.
Example:
AgNO₃ + NaCl → AgCl↓ + NaNO₃
AgCl is formed as a precipitate.
Q16. What is oxidation?
Oxidation can be defined as addition of oxygen or removal of hydrogen.
Example:
2Cu + O₂ → 2CuO
Copper gains oxygen.
Therefore copper is oxidised.
Q17. What is reduction?
Reduction is removal of oxygen or addition of hydrogen.
CuO + H₂ → Cu + H₂O
CuO loses oxygen.
Therefore CuO is reduced.
Q18. What is a redox reaction?
A reaction in which oxidation and reduction occur simultaneously is
called a redox reaction.
Example:
CuO + H₂ → Cu + H₂O
CuO is reduced and H₂ is oxidised.
Q19. Identify oxidation and reduction in CuO + H₂ → Cu + H₂O.
CuO loses oxygen:
CuO → Cu
Therefore CuO is reduced.
H₂ gains oxygen:
H₂ → H₂O
Therefore H₂ is oxidised.
CuO → Cu
Therefore CuO is reduced.
H₂ gains oxygen:
H₂ → H₂O
Therefore H₂ is oxidised.
Q20. What is an exothermic reaction?
A reaction which releases heat is called an exothermic reaction.
Example:
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat
Heat is released.
Therefore combustion of methane is exothermic.
Q21. What is an endothermic reaction?
A reaction which absorbs energy from surroundings is called an
endothermic reaction.
Example:
CaCO₃ + Heat → CaO + CO₂
Heat is required for decomposition.
Q22. What is corrosion?
Corrosion is the slow deterioration of a metal due to reaction with
environmental substances such as oxygen and moisture.
Example:
Rusting of iron.
हिन्दी: वातावरण के प्रभाव से धातु का धीरे-धीरे खराब होना संक्षारण कहलाता है।
हिन्दी: वातावरण के प्रभाव से धातु का धीरे-धीरे खराब होना संक्षारण कहलाता है।
Q23. How can rusting of iron be prevented?
Rusting requires oxygen and moisture.
Therefore prevent contact with oxygen and water.
Methods:
1. Painting
2. Oiling or greasing
3. Galvanisation
4. Alloying
Methods:
1. Painting
2. Oiling or greasing
3. Galvanisation
4. Alloying
Q24. What is rancidity?
Oxidation of fats and oils which causes unpleasant smell and taste is
called rancidity.
Q25. Why are chips packets filled with nitrogen?
Step 1:
Oils and fats undergo oxidation.
Step 2: Oxidation causes rancidity.
Step 3: Nitrogen is comparatively unreactive and prevents contact with oxygen.
Answer: Nitrogen is filled in chips packets to prevent oxidation of fats and oils and hence prevent rancidity.
Step 2: Oxidation causes rancidity.
Step 3: Nitrogen is comparatively unreactive and prevents contact with oxygen.
Answer: Nitrogen is filled in chips packets to prevent oxidation of fats and oils and hence prevent rancidity.
Q26. Why does silver turn black?
Silver reacts with sulphur compounds present in air.
A black coating of silver sulphide forms on the surface.
Therefore silver articles turn black.
A black coating of silver sulphide forms on the surface.
Therefore silver articles turn black.
Q27. Why does copper develop a green coating?
Copper reacts with moist air and carbon dioxide.
A green layer of basic copper carbonate forms.
Therefore copper develops a green coating.
A green layer of basic copper carbonate forms.
Therefore copper develops a green coating.
Q28. Write the reaction between iron and copper sulphate.
Reactants:
Fe + CuSO₄
Iron is more reactive than copper. Therefore Fe displaces Cu.
Iron is more reactive than copper. Therefore Fe displaces Cu.
Fe + CuSO₄ → FeSO₄ + Cu
With physical states:
Fe(s) + CuSO₄(aq)
→ FeSO₄(aq) + Cu(s)
Q29. A solution changes colour when iron is placed in CuSO₄.
Explain.
Initially CuSO₄ solution is blue.
Iron displaces copper:
Therefore the blue colour changes due to formation of FeSO₄.
Iron displaces copper:
Fe + CuSO₄ → FeSO₄ + Cu
FeSO₄ solution is pale green.
Therefore the blue colour changes due to formation of FeSO₄.
Q30. What is a precipitate?
An insoluble solid formed during a chemical reaction in a solution
is called a precipitate.
Example:
AgNO₃ + NaCl → AgCl↓ + NaNO₃
AgCl is the white precipitate.
Q31. Balance: Al + O₂ → Al₂O₃.
O atoms in Al₂O₃ = 3.
LCM of 2 and 3 = 6.
Put 3 before O₂ and 2 before Al₂O₃.
Al + 3O₂ → 2Al₂O₃
Now Al atoms = 4.
Put 4 before Al.
4Al + 3O₂ → 2Al₂O₃
Final Answer:
4Al + 3O₂ → 2Al₂O₃
Q32. Balance: Na + H₂O → NaOH + H₂.
Put 2 before Na and H₂O.
2Na + 2H₂O → 2NaOH + H₂
Check:
Na = 2 on both sides.
O = 2 on both sides.
H = 4 on both sides.
Therefore balanced.
Q33. Balance: Pb(NO₃)₂ + KI → PbI₂ + KNO₃.
PbI₂ contains 2 iodine atoms.
Put 2 before KI.
Pb(NO₃)₂ + 2KI → PbI₂ + KNO₃
Now K = 2. Put 2 before KNO₃.
Pb(NO₃)₂ + 2KI → PbI₂ + KNO₃
Now K = 2. Put 2 before KNO₃.
Pb(NO₃)₂ + 2KI
→ PbI₂ + 2KNO₃
Balanced equation.
Q34. Explain why respiration is an exothermic process.
During respiration, glucose reacts with oxygen and releases energy.
C₆H₁₂O₆ + 6O₂
→ 6CO₂ + 6H₂O + Energy
Since energy is released, respiration is an exothermic process.
Q35. What are the signs of a chemical reaction?
Important observations are:
1. Change in colour.
2. Change in temperature.
3. Evolution of gas.
4. Formation of precipitate.
5. Change in state.
1. Change in colour.
2. Change in temperature.
3. Evolution of gas.
4. Formation of precipitate.
5. Change in state.
Q36. Why is the burning of magnesium considered a combination reaction?
Two reactants combine:
Mg + O₂
Only one product is formed:
MgO
Therefore it is a combination reaction.
Mg + O₂
Only one product is formed:
MgO
Therefore it is a combination reaction.
2Mg + O₂ → 2MgO
Q37. Classify the reaction:
CaCO₃ → CaO + CO₂.
There is one reactant.
There are two products.
Therefore one compound is breaking into simpler substances.
Answer: It is a decomposition reaction.
There are two products.
Therefore one compound is breaking into simpler substances.
Answer: It is a decomposition reaction.
Q38. Classify:
Fe + CuSO₄ → FeSO₄ + Cu.
Fe replaces Cu from CuSO₄.
Therefore it is a displacement reaction.
Q39. Classify:
AgNO₃ + NaCl → AgCl + NaNO₃.
The ions exchange partners.
Ag⁺ combines with Cl⁻.
Na⁺ combines with NO₃⁻.
Therefore it is a double displacement reaction.
AgCl forms a precipitate.
Q40. Explain the law of conservation of mass using a chemical equation.
Consider:
Product side: H = 4 atoms O = 2 atoms
Therefore atoms are conserved. Hence the equation obeys the law of conservation of mass.
2H₂ + O₂ → 2H₂O
Reactant side:
H = 4 atoms
O = 2 atoms
Product side: H = 4 atoms O = 2 atoms
Therefore atoms are conserved. Hence the equation obeys the law of conservation of mass.
Q41. Assertion: Chemical equations must be balanced.
Reason: Atoms cannot be created or destroyed.
Both statements are true.
The reason correctly explains the assertion because balancing ensures
equal number of atoms on both sides.
Q42. Assertion: Respiration is exothermic.
Reason: Energy is released during respiration.
Both Assertion and Reason are true.
Reason correctly explains why respiration is exothermic.
Q43. Assertion: Chips packets are filled with nitrogen.
Reason: Nitrogen prevents oxidation.
Both statements are correct.
Nitrogen reduces the availability of oxygen and therefore slows
oxidation of fats and oils.
Q44. Case: A student heats CaCO₃ strongly. What happens?
On heating, calcium carbonate decomposes.
1. Reactant = CaCO₃.
2. Heat is supplied.
3. CaCO₃ breaks down.
4. CaO and CO₂ are formed.
5. Therefore it is thermal decomposition.
CaCO₃(s) → CaO(s) + CO₂(g)
Step-by-step:
1. Reactant = CaCO₃.
2. Heat is supplied.
3. CaCO₃ breaks down.
4. CaO and CO₂ are formed.
5. Therefore it is thermal decomposition.
Q45. Case: Pb(NO₃)₂ reacts with KI. Explain the observation.
Lead nitrate reacts with potassium iodide.
Pb(NO₃)₂ + 2KI
→ PbI₂↓ + 2KNO₃
PbI₂ is insoluble.
Therefore a yellow precipitate is formed.
This is a double displacement reaction.
Q46. Write five observations that indicate a chemical reaction.
Step 1: Change in colour.
Step 2: Evolution of gas.
Step 3: Formation of precipitate.
Step 4: Change in temperature.
Step 5: Change in physical state.
Step 2: Evolution of gas.
Step 3: Formation of precipitate.
Step 4: Change in temperature.
Step 5: Change in physical state.
Q47. Explain oxidation and reduction using one reaction.
Consider:
H₂ gains oxygen. Therefore H₂ is oxidised.
Both occur simultaneously. Hence the reaction is redox.
CuO + H₂ → Cu + H₂O
CuO loses oxygen.
Therefore CuO is reduced.
H₂ gains oxygen. Therefore H₂ is oxidised.
Both occur simultaneously. Hence the reaction is redox.
Q48. Explain corrosion and two methods of preventing it.
Corrosion is gradual destruction of a metal by environmental factors.
Example: rusting of iron.
Method 1: Painting prevents contact with oxygen and moisture.
Method 2: Galvanisation provides a protective zinc coating.
Example: rusting of iron.
Method 1: Painting prevents contact with oxygen and moisture.
Method 2: Galvanisation provides a protective zinc coating.
Q49. Explain rancidity and three methods of prevention.
Rancidity is oxidation of fats and oils.
It can be prevented by:
1. Refrigeration.
2. Airtight packaging.
3. Adding antioxidants.
4. Nitrogen flushing.
Nitrogen-filled packaging is commonly used for chips and similar food products.
It can be prevented by:
1. Refrigeration.
2. Airtight packaging.
3. Adding antioxidants.
4. Nitrogen flushing.
Nitrogen-filled packaging is commonly used for chips and similar food products.
Q50. Write a complete chemical equation and explain every part.
Consider:
Step 2 – Products: ZnCl₂ and H₂ are products.
Step 3 – Physical states: Zn(s) = solid.
HCl(aq) = aqueous solution.
ZnCl₂(aq) = aqueous solution.
H₂(g) = gas.
Step 4 – Balancing: Zn atoms = 1 on both sides. Cl atoms = 2 on both sides. H atoms = 2 on both sides. Therefore the equation is balanced.
Step 5 – Reaction type: Zn displaces hydrogen from HCl. Therefore it is a displacement reaction.
Zn(s) + 2HCl(aq)
→ ZnCl₂(aq) + H₂(g)
Step 1 – Reactants:
Zn and HCl are reactants.
Step 2 – Products: ZnCl₂ and H₂ are products.
Step 3 – Physical states: Zn(s) = solid.
HCl(aq) = aqueous solution.
ZnCl₂(aq) = aqueous solution.
H₂(g) = gas.
Step 4 – Balancing: Zn atoms = 1 on both sides. Cl atoms = 2 on both sides. H atoms = 2 on both sides. Therefore the equation is balanced.
Step 5 – Reaction type: Zn displaces hydrogen from HCl. Therefore it is a displacement reaction.
Final Board Answer:
A complete chemical equation represents reactants, products and their
physical states symbolically. For example:
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
Here Zn and HCl are reactants, ZnCl₂ and H₂ are products, and (s), (aq), and (g) represent their physical states. The equation is balanced and represents a displacement reaction.
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
Here Zn and HCl are reactants, ZnCl₂ and H₂ are products, and (s), (aq), and (g) represent their physical states. The equation is balanced and represents a displacement reaction.
7️⃣ Final Board Revision / अंतिम पुनरावृत्ति
CBSE में इन points को जरूर याद करें:
1. Chemical reaction की definition.
2. Reactants और products.
3. Chemical equation.
4. Balanced chemical equation.
5. Law of conservation of mass.
6. Physical state symbols.
7. Combination reaction.
8. Decomposition reaction.
9. Displacement reaction.
10. Double displacement reaction.
11. Oxidation.
12. Reduction.
13. Redox reaction.
14. Exothermic reaction.
15. Corrosion.
16. Rancidity.
1. Chemical reaction की definition.
2. Reactants और products.
3. Chemical equation.
4. Balanced chemical equation.
5. Law of conservation of mass.
6. Physical state symbols.
7. Combination reaction.
8. Decomposition reaction.
9. Displacement reaction.
10. Double displacement reaction.
11. Oxidation.
12. Reduction.
13. Redox reaction.
14. Exothermic reaction.
15. Corrosion.
16. Rancidity.
2Mg(s) + O₂(g) → 2MgO(s)
Zn(s) + 2HCl(aq)
→ ZnCl₂(aq) + H₂(g)
Fe(s) + CuSO₄(aq)
→ FeSO₄(aq) + Cu(s)
AgNO₃(aq) + NaCl(aq)
→ AgCl(s)↓ + NaNO₃(aq)
CaCO₃(s) → CaO(s) + CO₂(g)
