Class XI Chemistry Thermodynamics 2

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Question 1

Which of the following statements is correct about heat of combustion–

• AIt may be exothermic in some cases and endothermic in other cases
• BIt is applicable to gaseous substances only
• CIt is always an exothermic reaction
• DIts value does not change with temperature

Question 2

Values of heats of formation for SiO₂ and MgO are – 48.4 and – 34.7 kJ respectively. The heat of the reaction
2Mg + SiO₂→ 2MgO + Si is -

• A62.10 kJ
• B– 62.10 kJ
• C– 13.7 kJ
• D13.7 kJ

Question 3

A steam engine is operating between the temperature 25 ºC and 140 ºC. The maximum efficiency of engine is–

• A100%
• B50%
• C25%
• D27.8%

Question 4

When heat is supplied to an ideal gas in an isothermal process, the -

• AGas will do positive work
• BGas will do negative work
• CKinetic energy of gas will increase
• DGas will not obey the law of conservation of energy

Question 5

Which is the intensive property -

• ATemperature
• BViscosity
• CDensity
• DAll

Question 6

H₂ + 1/2 O₂→H₂O ; ΔH = – 68.39 kcal
K+H₂O → KOH(aq.)+H₂;ΔH= – 48 kcal
KOH + water → KOH (aq.);
ΔH = – 14 kcal
The heat of formation of KOH (in kcal) is–

• A– 68.39 + 48 – 14
• B– 68.39 – 48 + 14
• C68.39 – 48 + 14
• D68.39 + 48 + 14

Question 7

Difference between ΔH and ΔU for the combustion of benzene at 300 K is –

• A7.48 kJ
• B3.74 kJ
• C14.86 kJ
• D5.73 kJ

Question 8

Enthalpy of vaporization of water is 40800 J mol^–1 at atm pressure. The mountain where, the pressure is 380 mm of Hg, water will boil at–

• A100 ºC
• B81.6 ºC
• C104 ºC
• D50 ºC

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