In any chemical reaction, a quantity that decrease to a minimum i

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 Multiple Choice QuestionsMultiple Choice Questions

231.

Born-Haber cycle may be used to calculate

  • electronegativity

  • mass number

  • oxidation number

  • electron affinity


232.

The heat of formation for CO2 (g), H2O (l) and CH4 (g) are -400 kJ mol-1, -280 kJ mol-1 and -70 kJ mol-1 respectively. The heat of combustion of CH4 in kJ mol-1 is

  • 890

  • -160

  • -890

  • -90


233.

C (s) + O2 (g) → CO2 (g); H = -94kcal

2CO (g) + O2 (g) → 2CO2 (g); H = -135 kcal.

The heat of formation of CO (g) is

  • -26.4 kcal

  • 41.2 kcal

  • 26.4 kcal

  • 229.2 kcal


234.

The entropy of a perfectly crystalline material is zero at 0°C. This is statement of

  • first law of thermodynamics

  • second law of thermodynamics

  • third law of thermodynamics

  • law of conservation of energy


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235.

In any chemical reaction, a quantity that decrease to a minimum is

  • free energy

  • entropy

  • temperature

  • enthalpy


A.

free energy

For a spontaneous process, Gibbs free energy, ΔG < 0.

Hence, for a spontaneous chemicalreaction, free energy must be negative or in other words free energy is the quantity that decreases to a minimum in any chemical reaction.


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236.

Given, H2O (l) → H2O (g); H1 = +43 kJ

H2O (s) → H2O (l); H2 = +6.05 kJ. Calculate the enthalpy of sublimation of ice.

  • 49.75 kJ mol-1

  • 37.65 kJ mol-1

  • 43.7 kJ mol-1

  • 55.23 kJ mol-1


237.

If standard enthalpies of formation of CaCl (s) (hypothetical) and that of CaCl(s) are -188 J mol-1 and -795 kJ mol-1 respectively, calculate the value of standard heat of reaction for the following  disproportionation reaction

2CaCl (s) → CaCl2 (s) + Ca (s)

  • -607 kJ mol-1

  • +607 kJ mol-1

  • -419 kJ mol-1

  • +419 kJ mol-1


238.

Heat formation of H2O is -188 kJ/ mol and H2O2 is 286 kJ/mol. The enthalpy change for the reaction; 2H2O2 → 2H2O + O2 is

  • 196 kJ

  • -196 kJ

  • 984 kJ

  • -984 kJ


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239.

When 1 mole of a gas is heated at constant volume, temperature is raised from 298 K to 308 K. Heat supplied to the gas is 500J. Then, which statement is correct?

  • q= -W = 500J : ΔE= 0

  • q= W = 500J : ΔE= 0

  • q = ΔE= 500J , W= 0

  • ΔE = 0; q= W = -500J


240.

If enthaplies of formation for C2H2(g), CO2(g) and H2O(l) at 25°C and 1atm pressure be 52, -394 and -286kJ mol-1 respectively, then the enthaply of combustion of C2H4(g) will be

  • -141.2 kJ mol-1

  • -1412 kJ mol-1

  • + 141.2 kJ mol-1

  • + 1412 kJ mol-1


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