Define Henry’s Law and explain why the solubility of a gas decreases with increasing temperature.

1. Define Henry’s Law and explain why the solubility of a gas decreases with increasing temperature. 1. हेनरी के नियम को परिभाषित कीजिए तथा समझाइए कि तापमान बढ़ने पर गैस की विलेयता क्यों कम हो जाती है। +

Detailed Answer

Henry’s Law states that at constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the solution.

C ∝ P

C = k_HP

Where:

C = concentration or solubility of the dissolved gas
P = partial pressure of the gas
k_H = Henry’s law constant

Thus, if the partial pressure of a gas increases, more gas dissolves in the liquid, provided the temperature remains constant.

Effect of Temperature on Gas Solubility

The solubility of most gases in liquids decreases when temperature increases.

This happens mainly because the dissolution of gases in liquids is generally an exothermic process. When the temperature is increased, heat is supplied to the system.

According to Le Chatelier’s principle, the equilibrium shifts in the direction that absorbs the added heat. Therefore, the dissolved gas tends to escape from the liquid into the gaseous phase.

Temperature ↑
↓
Kinetic energy of gas molecules ↑
↓
Gas molecules escape more easily from the liquid
↓
Gas solubility ↓

Molecular Explanation

At higher temperatures, gas molecules possess greater kinetic energy. Therefore, the molecules move more rapidly and are more likely to overcome the attractive forces holding them in the liquid.

As a result, more dissolved gas molecules leave the liquid and enter the gas phase. Hence, the equilibrium concentration of the dissolved gas decreases.

Example

Carbon dioxide is much more soluble in cold water than in warm water. Therefore, cold carbonated drinks retain dissolved CO₂ better than warm drinks.

When a carbonated drink is warmed, CO₂ escapes more rapidly, which is why the drink loses its fizz.

Important Exception

The statement that gas solubility decreases with increasing temperature applies to most gases. The exact temperature dependence can vary depending on the gas, solvent and pressure conditions.

Final Answer

Henry’s Law states that at constant temperature, the solubility of a gas in a liquid is directly proportional to its partial pressure: C = k_HP. The solubility of most gases decreases with increasing temperature because gas dissolution is generally exothermic. Heating gives gas molecules more kinetic energy, causing them to escape more readily from the liquid into the gas phase. Therefore, the amount of dissolved gas decreases.

विस्तृत उत्तर

हेनरी का नियम (Henry’s Law) कहता है कि स्थिर तापमान पर किसी द्रव में घुली हुई गैस की विलेयता उस गैस के द्रव के ऊपर उपस्थित आंशिक दाब के समानुपाती होती है।

C ∝ P

C = k_HP

जहाँ:

C = द्रव में घुली गैस की सांद्रता/विलेयता
P = गैस का आंशिक दाब
k_H = हेनरी नियम नियतांक

अर्थात यदि तापमान स्थिर हो और गैस का आंशिक दाब बढ़ाया जाए, तो अधिक मात्रा में गैस द्रव में घुलेगी।

तापमान बढ़ने पर गैस की विलेयता क्यों घटती है?

अधिकांश गैसों की द्रवों में विलेयता तापमान बढ़ने पर कम हो जाती है।

इसका मुख्य कारण यह है कि गैसों का द्रव में घुलना सामान्यतः ऊष्माक्षेपी (exothermic) प्रक्रिया होती है। जब तापमान बढ़ाया जाता है, तो सिस्टम को ऊष्मा प्रदान की जाती है।

Le Chatelier के सिद्धांत के अनुसार equilibrium अतिरिक्त ऊष्मा के प्रभाव को कम करने वाली दिशा में shift करता है। इसलिए घुली हुई गैस द्रव से बाहर निकलकर गैसीय अवस्था में जाने लगती है।

तापमान ↑
↓
गैस अणुओं की गतिज ऊर्जा ↑
↓
अणु द्रव से आसानी से बाहर निकलते हैं
↓
गैस की विलेयता ↓

आणविक कारण

तापमान बढ़ने पर गैस के अणुओं की गतिज ऊर्जा बढ़ जाती है। इसके कारण अणु अधिक तेजी से गति करते हैं और द्रव में उन्हें रोकने वाले आकर्षण बलों को आसानी से पार कर सकते हैं।

इसलिए अधिक संख्या में घुले हुए गैस अणु द्रव से निकलकर गैस अवस्था में चले जाते हैं। परिणामस्वरूप द्रव में घुली गैस की मात्रा कम हो जाती है।

उदाहरण

ठंडे पानी में CO₂ की विलेयता गर्म पानी की तुलना में अधिक होती है। इसलिए cold carbonated drinks में CO₂ अधिक समय तक घुली रहती है।

जब carbonated drink को गर्म किया जाता है, तो CO₂ तेजी से बाहर निकलती है और drink की fizz कम हो जाती है।

महत्वपूर्ण बात

तापमान बढ़ने पर गैस की विलेयता घटने का नियम अधिकांश गैसों पर लागू होता है। वास्तविक प्रभाव गैस, विलायक और दबाव की परिस्थितियों पर निर्भर कर सकता है।

अंतिम उत्तर

हेनरी का नियम कहता है कि स्थिर तापमान पर द्रव में गैस की विलेयता उसके आंशिक दाब के समानुपाती होती है: C = k_HP. अधिकांश गैसों की विलेयता तापमान बढ़ने पर कम हो जाती है क्योंकि गैस का द्रव में घुलना सामान्यतः ऊष्माक्षेपी प्रक्रिया है। तापमान बढ़ने पर गैस अणुओं की गतिज ऊर्जा बढ़ती है और वे द्रव से अधिक आसानी से बाहर निकलते हैं। इसलिए द्रव में घुली गैस की मात्रा कम हो जाती है।

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30 Related MCQs 30 संबंधित बहुविकल्पीय प्रश्न

1. Henry’s Law relates the solubility of a gas to its:

A. Atomic mass

B. Partial pressure

C. Density

D. Melting point

Answer: B. Partial pressure

2. The mathematical expression of Henry’s Law is:

A. C = k_HP

B. PV = nRT

C. P = k/C

D. C = P²

Answer: A. C = k_HP

3. According to Henry’s Law, gas solubility increases when pressure:

A. Decreases

B. Increases

C. Becomes zero

D. Remains irrelevant

Answer: B. Increases

4. The solubility of most gases in liquids with increasing temperature:

A. Increases

B. Decreases

C. Remains exactly constant

D. Becomes infinite

Answer: B. Decreases

5. Dissolution of most gases in liquids is generally:

A. Endothermic

B. Exothermic

C. Nuclear

D. Photochemical

Answer: B. Exothermic

6. When temperature increases, gas molecules acquire:

A. Less kinetic energy

B. More kinetic energy

C. No energy

D. Constant zero energy

Answer: B. More kinetic energy

7. Carbon dioxide is more soluble in:

A. Warm water

B. Cold water

C. Boiling water

D. Hot oil

Answer: B. Cold water

8. Warm carbonated drinks lose CO₂ faster because:

A. Gas solubility increases

B. Gas solubility decreases

C. Pressure becomes infinite

D. CO₂ becomes solid

Answer: B. Gas solubility decreases

9. Henry’s Law is applicable at:

A. Constant temperature

B. Constant atomic number

C. Constant mass only

D. Zero pressure only

Answer: A. Constant temperature

10. k_H represents:

A. Henry’s law constant

B. Heat constant

C. Hydrogen constant

D. Kinetic constant

Answer: A. Henry’s law constant

11. Increasing the partial pressure of a gas generally causes its solubility to:

A. Increase

B. Decrease

C. Become zero

D. Remain unaffected

Answer: A. Increase

12. Which principle explains the effect of heat on an equilibrium involving gas dissolution?

A. Le Chatelier’s principle

B. Avogadro’s law

C. Graham’s law

D. Dalton’s law

Answer: A. Le Chatelier’s principle

13. On heating a gas-liquid solution, dissolved gas tends to:

A. Remain completely dissolved

B. Escape into the gas phase

C. Become a solid

D. React with all water molecules

Answer: B. Escape into the gas phase

14. Which gas is commonly used as an example of gas solubility in soft drinks?

A. CO₂

B. He

C. Ne

D. Ar

Answer: A. CO₂

15. The dissolved gas concentration is represented by:

A. C

B. P

C. T

D. V

Answer: A. C

16. If P doubles at constant temperature, according to Henry’s Law C will:

A. Halve

B. Double

C. Become zero

D. Remain unchanged

Answer: B. Double

17. The solubility of gases generally decreases because heating:

A. Reduces molecular motion

B. Increases molecular motion

C. Removes all solvent

D. Changes gas into a metal

Answer: B. Increases molecular motion

18. Which statement is correct?

A. Gas solubility always increases with temperature

B. Most gases become less soluble on heating

C. Gas solubility is independent of pressure

D. Henry’s Law applies only to solids

Answer: B. Most gases become less soluble on heating

19. A cold soft drink retains more CO₂ because:

A. CO₂ is more soluble at lower temperature

B. CO₂ becomes a solid

C. Water disappears

D. Pressure is always zero

Answer: A. CO₂ is more soluble at lower temperature

20. Heating a carbonated beverage causes:

A. More CO₂ dissolution

B. Faster CO₂ escape

C. Formation of nitrogen

D. Formation of oxygen

Answer: B. Faster CO₂ escape

21. Henry’s Law connects gas solubility with:

A. Partial pressure

B. Atomic radius

C. Ionization energy

D. Electronegativity

Answer: A. Partial pressure

22. The symbol P in Henry’s Law represents:

A. Temperature

B. Partial pressure

C. Mass

D. Volume

Answer: B. Partial pressure

23. Increasing temperature generally favours:

A. Retention of dissolved gas

B. Escape of dissolved gas

C. Solidification of gas

D. Formation of solvent

Answer: B. Escape of dissolved gas

24. Gas solubility is generally higher at:

A. Higher temperature

B. Lower temperature

C. Infinite temperature

D. Boiling point only

Answer: B. Lower temperature

25. The process of gas dissolving in liquid is generally:

A. Exothermic

B. Endothermic

C. Nuclear fission

D. Combustion

Answer: A. Exothermic

26. If gas pressure above a liquid is reduced, its solubility generally:

A. Increases

B. Decreases

C. Becomes infinite

D. Becomes independent of pressure

Answer: B. Decreases

27. Which factor does not directly appear in the simple Henry’s Law expression C = k_HP?

A. Gas partial pressure

B. Henry’s constant

C. Gas concentration

D. Atomic number

Answer: D. Atomic number

28. Why do gas molecules escape more easily at higher temperature?

A. Their kinetic energy increases

B. Their mass becomes zero

C. Their atomic number decreases

D. They become liquids

Answer: A. Their kinetic energy increases

29. Which statement about Henry’s Law is correct?

A. It states that gas solubility is proportional to partial pressure at constant temperature

B. It states that gas solubility is proportional to atomic number

C. It applies only to metals

D. It states that pressure has no effect

Answer: A. It states that gas solubility is proportional to partial pressure at constant temperature

30. The best reason for decreased gas solubility on heating is:

A. Gas molecules gain kinetic energy and escape from the liquid more readily

B. Gas molecules lose all kinetic energy

C. Pressure becomes zero in every case

D. Solvent mass becomes zero

Answer: A. Gas molecules gain kinetic energy and escape from the liquid more readily

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Explain why scuba divers use air diluted with helium to avoid the painful condition known as 'bends

1. Explain why scuba divers use air diluted with helium to avoid the painful condition known as 'bends'. 1. समझाइए कि स्कूबा डाइवर्स 'बेंड्स' नामक दर्दनाक स्थिति से बचने के लिए हीलियम से पतली की गई हवा का उपयोग क्यों करते हैं। +

Detailed Answer

Scuba divers breathe compressed air while diving deep underwater. This air usually contains nitrogen and oxygen. At great depths, the surrounding pressure becomes very high.

According to Henry's law, the solubility of a gas in a liquid increases when the pressure of that gas increases. Therefore, under high pressure, more nitrogen from the breathing air dissolves in the diver's blood and body tissues.

What happens during rapid ascent?

When a diver returns to the surface too quickly, the external pressure decreases rapidly. The nitrogen dissolved in the blood and tissues then comes out of solution and forms tiny gas bubbles.

These nitrogen bubbles can block blood vessels and damage tissues. They may cause severe pain in joints and muscles, breathing difficulty, dizziness, and other serious symptoms. This condition is called decompression sickness, commonly known as the 'bends'.

Why is Helium used?

Helium is used instead of a large proportion of nitrogen because helium is much less soluble in blood and body tissues than nitrogen.

Therefore, when helium is used in the breathing mixture, much less inert gas dissolves in the diver's tissues at high pressure.

During ascent, there is consequently a much smaller tendency for gas bubbles to form.

High Pressure → More N₂ dissolves in tissues
Rapid Ascent → N₂ bubbles form → Bends

Helium mixture → Less dissolved inert gas → Lower risk of bends

Why not simply use pure oxygen?

Pure oxygen is not normally used for deep diving because oxygen itself can become toxic at sufficiently high partial pressures. Therefore, specially prepared breathing mixtures such as helium–oxygen (Heliox) may be used for deep diving.

Helium is also chemically inert and has a low density, which makes breathing easier at great depths.

Role of Henry's Law

Henry's law explains the basic reason behind the bends:

At constant temperature, the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid.

C ∝ P
or
C = kP

Final Answer

Scuba divers use helium-diluted air because helium is less soluble in blood and tissues than nitrogen. At high pressure, less helium dissolves in the body, and during ascent there is less formation of gas bubbles. This reduces the risk of decompression sickness, commonly called the 'bends'.

विस्तृत उत्तर

स्कूबा डाइवर्स जब पानी के अंदर गहराई तक जाते हैं, तो वे संपीडित हवा (compressed air) में सांस लेते हैं। इस हवा में मुख्यतः नाइट्रोजन और ऑक्सीजन होती है। अधिक गहराई पर पानी का दबाव बहुत अधिक हो जाता है।

हेनरी के नियम (Henry's Law) के अनुसार किसी द्रव में गैस की विलेयता उस गैस के आंशिक दाब के बढ़ने पर बढ़ती है। इसलिए अधिक दबाव पर सांस लेने वाली हवा का अधिक नाइट्रोजन रक्त और शरीर के ऊतकों में घुल जाता है।

तेजी से ऊपर आने पर क्या होता है?

यदि गोताखोर बहुत तेजी से पानी की सतह की ओर आता है, तो बाहरी दबाव तेजी से कम हो जाता है। शरीर के ऊतकों और रक्त में घुला हुआ नाइट्रोजन गैस के रूप में बाहर निकलने लगता है और छोटे-छोटे बुलबुले बना सकता है।

ये नाइट्रोजन के बुलबुले रक्त वाहिकाओं को अवरुद्ध कर सकते हैं और ऊतकों को नुकसान पहुँचा सकते हैं। इससे जोड़ों और मांसपेशियों में तेज दर्द, चक्कर, सांस लेने में कठिनाई तथा अन्य गंभीर समस्याएँ हो सकती हैं। इस स्थिति को Decompression Sickness या सामान्य रूप से 'Bends' कहते हैं।

हीलियम का उपयोग क्यों किया जाता है?

हीलियम का उपयोग नाइट्रोजन के एक बड़े भाग के स्थान पर किया जाता है क्योंकि हीलियम रक्त और शरीर के ऊतकों में नाइट्रोजन की तुलना में बहुत कम घुलता है।

इसलिए उच्च दबाव पर शरीर में कम मात्रा में inert gas घुलती है। जब गोताखोर ऊपर आता है, तो गैस के बुलबुले बनने की संभावना कम हो जाती है।

अधिक दबाव → अधिक N₂ ऊतकों में घुलता है
तेजी से ऊपर आना → N₂ के बुलबुले → Bends

Helium mixture → कम घुली हुई inert gas → Bends का कम जोखिम

शुद्ध ऑक्सीजन का उपयोग क्यों नहीं?

बहुत अधिक गहराई पर ऑक्सीजन का आंशिक दाब बढ़ जाता है। पर्याप्त अधिक partial pressure पर ऑक्सीजन toxic प्रभाव उत्पन्न कर सकती है। इसलिए deep diving में उपयुक्त breathing mixtures, जैसे Heliox (helium + oxygen), का उपयोग किया जा सकता है।

हीलियम एक रासायनिक रूप से निष्क्रिय गैस है और इसकी density कम होने के कारण अधिक गहराई पर सांस लेना भी अपेक्षाकृत आसान होता है।

हेनरी के नियम की भूमिका

हेनरी का नियम bends को समझने में महत्वपूर्ण है। इसके अनुसार स्थिर तापमान पर किसी द्रव में गैस की विलेयता उस गैस के आंशिक दाब के समानुपाती होती है।

C ∝ P
या
C = kP

अंतिम उत्तर

स्कूबा डाइवर्स हीलियम से मिश्रित हवा का उपयोग इसलिए करते हैं क्योंकि हीलियम नाइट्रोजन की तुलना में रक्त और ऊतकों में कम घुलता है। अधिक दबाव पर शरीर में कम inert gas घुलती है और ऊपर आते समय गैस के बुलबुले बनने की संभावना कम हो जाती है। इससे Decompression Sickness या 'Bends' का खतरा कम होता है।

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30 Related MCQs 30 संबंधित बहुविकल्पीय प्रश्न

1. The painful condition commonly known as 'bends' is:

A. Hypothermia

B. Decompression sickness

C. Heat stroke

D. Anaemia

Answer: B. Decompression sickness

2. Which gas mainly causes the bends?

A. Oxygen

B. Hydrogen

C. Nitrogen

D. Helium

Answer: C. Nitrogen

3. Which law explains the increased solubility of nitrogen at high pressure?

A. Boyle's law

B. Charles' law

C. Henry's law

D. Graham's law

Answer: C. Henry's law

4. According to Henry's law, gas solubility is proportional to:

A. Temperature only

B. Partial pressure of gas

C. Volume of container

D. Molecular mass only

Answer: B. Partial pressure of gas

5. At greater underwater depth, pressure:

A. Decreases

B. Remains zero

C. Increases

D. Becomes negative

Answer: C. Increases

6. At high pressure, more nitrogen tends to:

A. Escape from blood

B. Dissolve in tissues

C. React chemically with water

D. Become oxygen

Answer: B. Dissolve in tissues

7. The gas used to replace much of nitrogen in deep-diving mixtures is:

A. Carbon dioxide

B. Helium

C. Chlorine

D. Neon

Answer: B. Helium

8. Helium is preferred because it is relatively:

A. Highly reactive

B. Toxic

C. Inert

D. Combustible

Answer: C. Inert

9. Helium is less soluble in body tissues than:

A. Nitrogen

B. Oxygen

C. Hydrogen

D. Fluorine

Answer: A. Nitrogen

10. Rapid ascent from deep water causes pressure to:

A. Increase rapidly

B. Decrease rapidly

C. Remain constant

D. Become infinite

Answer: B. Decrease rapidly

11. During rapid ascent, dissolved nitrogen may form:

A. Solid particles

B. Gas bubbles

C. Salts

D. Water droplets

Answer: B. Gas bubbles

12. Gas bubbles formed during decompression can:

A. Improve circulation

B. Block blood vessels

C. Increase oxygen production

D. Produce water

Answer: B. Block blood vessels

13. A mixture of helium and oxygen is called:

A. Nitrox

B. Heliox

C. Syngas

D. Producer gas

Answer: B. Heliox

14. Helium has a relatively:

A. High density

B. Low density

C. Very high toxicity

D. High reactivity

Answer: B. Low density

15. Which gas is chemically inert?

A. Helium

B. Oxygen

C. Chlorine

D. Hydrogen

Answer: A. Helium

16. The main gas responsible for nitrogen narcosis is:

A. Nitrogen

B. Helium

C. Oxygen

D. Argon

Answer: A. Nitrogen

17. The solubility of a gas in a liquid generally increases when pressure:

A. Increases

B. Decreases

C. Becomes zero

D. Is irrelevant

Answer: A. Increases

18. Henry's law is related to:

A. Solubility of gases in liquids

B. Atomic radius

C. Ionization energy

D. Chemical equilibrium only

Answer: A. Solubility of gases in liquids

19. The concentration of dissolved gas is represented by:

A. C

B. P only

C. T only

D. V only

Answer: A. C

20. The Henry's law relation can be written as:

A. C = kP

B. PV = nRT

C. E = mc²

D. P = F/A

Answer: A. C = kP

21. Why is pure oxygen not generally used for deep diving?

A. It is always insoluble

B. High oxygen partial pressure can become toxic

C. It has no oxygen atoms

D. It freezes immediately

Answer: B. High oxygen partial pressure can become toxic

22. Helium is classified as a:

A. Noble gas

B. Halogen

C. Alkali metal

D. Chalcogen

Answer: A. Noble gas

23. Helium belongs to:

A. Group 1

B. Group 2

C. Group 17

D. Group 18

Answer: D. Group 18

24. The 'bends' are primarily associated with:

A. Rapid decompression

B. Slow heating

C. Freezing

D. Low humidity

Answer: A. Rapid decompression

25. Which factor determines the amount of gas dissolved according to Henry's law?

A. Partial pressure

B. Atomic number

C. Neutron number

D. Crystal structure

Answer: A. Partial pressure

26. Deep-sea divers experience higher pressure mainly because of:

A. Water column above them

B. Atmospheric heating

C. Sunlight

D. Wind

Answer: A. Water column above them

27. Which mixture may be used for deep diving?

A. Helium + oxygen

B. Chlorine + oxygen

C. Fluorine + oxygen

D. Hydrogen + chlorine

Answer: A. Helium + oxygen

28. The bubbles responsible for decompression sickness are mainly:

A. Nitrogen bubbles

B. Helium crystals

C. Oxygen solids

D. Water bubbles

Answer: A. Nitrogen bubbles

29. Which property of helium makes it useful as a deep-diving gas?

A. High chemical reactivity

B. Low density and low solubility compared with nitrogen

C. High toxicity

D. Ability to burn

Answer: B. Low density and low solubility compared with nitrogen

30. The best explanation for using helium in deep-diving breathing mixtures is:

A. It increases nitrogen absorption

B. It reduces the amount of nitrogen dissolving in tissues

C. It produces oxygen inside the lungs

D. It increases water pressure

Answer: B. It reduces the amount of nitrogen dissolving in tissues

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Why is molality (m) preferred over molarity (M) when expressing concentrations at varying temperatures?

1. Why is molality (m) preferred over molarity (M) when expressing concentrations at varying temperatures? 1. विभिन्न तापमानों पर सांद्रता व्यक्त करते समय मोलैलिटी (m) को मोलैरिटी (M) की अपेक्षा क्यों प्राथमिकता दी जाती है? +

Detailed Answer

Molality (m) is preferred over molarity (M) when concentration needs to be compared at different temperatures because molality depends on the mass of the solvent, whereas molarity depends on the volume of the solution.

Molality = Number of moles of solute / Mass of solvent in kg

m = n / W

Molarity = Number of moles of solute / Volume of solution in litre

M = n / V

Why is Molality Temperature Independent?

Temperature can change the volume of a substance because of thermal expansion or contraction. Therefore, the volume of a solution may change when temperature changes.

Since molarity is based on the volume of solution, its value may change with temperature.

However, the mass of solvent does not appreciably change with temperature. Therefore, molality remains essentially constant with temperature.

Hence, molality is preferred when concentration has to be expressed or compared at varying temperatures.

Key Difference

Molality: Based on mass of solvent → essentially independent of temperature.

Molarity: Based on volume of solution → changes with temperature.

Conclusion

Molality is preferred over molarity for temperature-dependent studies because mass remains essentially constant with temperature, whereas the volume of a solution changes with temperature.

विस्तृत उत्तर

मोलैलिटी (m) को मोलैरिटी (M) की अपेक्षा विभिन्न तापमानों पर सांद्रता व्यक्त करने के लिए अधिक उपयुक्त माना जाता है, क्योंकि मोलैलिटी विलायक के द्रव्यमान पर आधारित होती है, जबकि मोलैरिटी विलयन के आयतन पर आधारित होती है।

मोलैलिटी = विलेय के मोल / विलायक का द्रव्यमान (kg)

m = n / W

मोलैरिटी = विलेय के मोल / विलयन का आयतन (L)

M = n / V

मोलैलिटी तापमान पर निर्भर क्यों नहीं होती?

तापमान बदलने पर पदार्थों के आयतन में प्रसार या संकुचन हो सकता है। इसलिए विलयन का आयतन तापमान के साथ बदल सकता है।

चूँकि मोलैरिटी विलयन के आयतन पर निर्भर करती है, इसलिए तापमान बदलने पर इसकी मात्रा बदल सकती है।

इसके विपरीत, विलायक का द्रव्यमान तापमान बदलने पर सामान्यतः नहीं बदलता। इसलिए मोलैलिटी तापमान से लगभग स्वतंत्र रहती है।

इसी कारण अलग-अलग तापमानों पर सांद्रता की तुलना करने के लिए मोलैलिटी अधिक विश्वसनीय है।

मुख्य अंतर

मोलैलिटी: विलायक के द्रव्यमान पर आधारित → तापमान से लगभग स्वतंत्र।

मोलैरिटी: विलयन के आयतन पर आधारित → तापमान के साथ बदल सकती है।

निष्कर्ष

विभिन्न तापमानों पर सांद्रता की तुलना के लिए मोलैलिटी को प्राथमिकता दी जाती है क्योंकि द्रव्यमान तापमान से लगभग अपरिवर्तित रहता है, जबकि विलयन का आयतन तापमान के साथ बदल सकता है।

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30 Related MCQs 30 संबंधित बहुविकल्पीय प्रश्न

1. Which concentration term is independent of temperature?

A. Molarity

B. Molality

C. Normality

D. Volume percentage

Answer: B. Molality

2. Molality is defined as moles of solute per:

A. Litre of solution

B. Litre of solvent

C. Kilogram of solvent

D. Kilogram of solution

Answer: C. Kilogram of solvent

3. Molarity is expressed as:

A. mol kg⁻¹

B. mol L⁻¹

C. kg mol⁻¹

D. L mol⁻¹

Answer: B. mol L⁻¹

4. Molality is expressed as:

A. mol L⁻¹

B. mol kg⁻¹

C. kg mol⁻¹

D. L mol⁻¹

Answer: B. mol kg⁻¹

5. Which quantity changes with temperature?

A. Mass of solvent

B. Number of moles

C. Volume of solution

D. Molecular mass

Answer: C. Volume of solution

6. Why can molarity change with temperature?

A. Moles change

B. Molecular mass changes

C. Solution volume changes

D. Solute disappears

Answer: C. Solution volume changes

7. Molality depends on the mass of:

A. Solute

B. Solvent

C. Solution

D. Container

Answer: B. Solvent

8. Molarity depends on the volume of:

A. Solute

B. Solvent

C. Solution

D. Gas only

Answer: C. Solution

9. Which concentration unit is most suitable for colligative property calculations?

A. Molality

B. Molarity only

C. Volume percentage

D. Mole fraction only

Answer: A. Molality

10. The SI-related unit commonly used for molality is:

A. mol L⁻¹

B. mol kg⁻¹

C. kg L⁻¹

D. L kg⁻¹

Answer: B. mol kg⁻¹

11. If temperature increases, the volume of most solutions generally:

A. Decreases

B. Increases

C. Becomes zero

D. Remains exactly unchanged

Answer: B. Increases

12. Which concentration is based on kg of solvent?

A. Molarity

B. Molality

C. Formality

D. Volume fraction

Answer: B. Molality

13. Which concentration is based on litres of solution?

A. Molality

B. Molarity

C. Mole fraction

D. Mass fraction

Answer: B. Molarity

14. If 1 mole of solute is dissolved in 1 kg solvent, molality is:

A. 0.1 m

B. 1 m

C. 10 m

D. 100 m

Answer: B. 1 m

15. Which quantity remains essentially constant when temperature changes?

A. Solution volume

B. Solvent mass

C. Density

D. Molarity

Answer: B. Solvent mass

16. The symbol for molality is:

A. M

B. m

C. N

D. X

Answer: B. m

17. The symbol for molarity is:

A. m

B. M

C. X

D. W

Answer: B. M

18. Which one is a temperature-independent concentration unit?

A. Molarity

B. Molality

C. Volume percentage

D. Normality based on volume

Answer: B. Molality

19. For accurate comparison of solutions at different temperatures, one should prefer:

A. Molarity

B. Molality

C. Volume fraction

D. Density only

Answer: B. Molality

20. Molality is calculated using:

A. Moles / volume

B. Moles / mass of solvent

C. Mass / volume

D. Volume / moles

Answer: B. Moles / mass of solvent

21. Which factor causes the volume of solution to change?

A. Temperature

B. Atomic number only

C. Proton number

D. Neutron number

Answer: A. Temperature

22. Molality is particularly useful in:

A. Colligative properties

B. Atomic structure only

C. Nuclear reactions only

D. Periodic classification only

Answer: A. Colligative properties

23. If 2 moles solute are dissolved in 4 kg solvent, molality is:

A. 0.25 m

B. 0.5 m

C. 2 m

D. 8 m

Answer: B. 0.5 m

24. If the volume of a solution increases while moles remain constant, its molarity:

A. Increases

B. Decreases

C. Remains same

D. Becomes infinite

Answer: B. Decreases

25. Which statement is correct?

A. Molality depends on solution volume

B. Molarity depends on solvent mass

C. Molality depends on solvent mass

D. Both depend only on temperature

Answer: C. Molality depends on solvent mass

26. Which concentration unit is represented by mol kg⁻¹?

A. Molarity

B. Molality

C. Normality

D. Mole fraction

Answer: B. Molality

27. Which concentration unit is represented by mol L⁻¹?

A. Molality

B. Molarity

C. Mole fraction

D. Mass fraction

Answer: B. Molarity

28. The denominator in molality contains:

A. Volume of solution

B. Mass of solvent

C. Mass of solute

D. Volume of solute

Answer: B. Mass of solvent

29. The denominator in molarity contains:

A. Mass of solvent

B. Mass of solute

C. Volume of solution

D. Volume of solvent only

Answer: C. Volume of solution

30. Why is molality preferred over molarity at varying temperatures?

A. It depends on solution volume

B. It depends on solvent mass

C. It depends on density only

D. It depends on temperature directly

Answer: B. It depends on solvent mass

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