For the reaction, X2Y4 (l) → 2XY2 (g) at 300 K, the values o

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 Multiple Choice QuestionsMultiple Choice Questions

31.

Which of the following plots represent an exothermic reaction?


32.

The condition for a reaction to occur spontaneously is

  • H must be negative

  • S must be negative

  • H-TS must be negative

  • H+TS must be negative


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33.

For the reaction, X2Y4 (l) → 2XY2 (g) at 300 K, the values of U and S are 2 kcal and 20 cal K-1 respectively. The value of G for the reaction is

  • -3400 cal

  • 3400 cal

  • -2800 cal

  • 2000 cal


C.

-2800 cal

For the reaction X2Y2 (l) → 2XY2 (g)

ng = number of gaseous products - number of gaseous reactants

ng = 2 - 0 = 2

Given that, U = 2kcal

S = 20 cal K-1

From the formula, 

H = U + ngRT

Putting the value, we get

H = 2 + 2 × 2 × 3001000

      = 3.2 kcal = 3.2 × 103 cal

Also, G = H - TS

              = 3.2 × 103 - 300 × 20

              = 3.2 × 103 - 6 × 103

              = -2800 cal


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34.

The values of H and S of a certain reaction are -400 kJ mol-1 and -20 kJ mol-1K-1 respectively. The temperature below which the reaction is spontaneous, is

  • 100 K

  • 20°C

  • 20 K

  • 120°C


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35.

The enthalpy of vaporisation of a certain liquid at its boiling point of 35°C is 24.64 kJ mol-1. The value of change in entropy for the process is

  • 704 JK -1mol-1

  • 80 JK -1mol-1

  • 24.64 JK -1mol-1

  • 7.04 JK-1mol-1


36.

Given that

C + O2  CO2; H°= -x kJ2CO + O2 2CO2; H°= -y kJ

The heat of formation of carbon monoxide will be

  • y- 2x2

  • y + 2x

  • 2x - y 

  • 2x-y2


37.

The value of H for cooling 2 mole of an ideal monoatomic gas from 225°C to 125°C at constant pressure will be [ given Cp52R].

  • 250 R

  • -500 R

  • 500R

  • -250 R


38.

The change of entropy (dS) is defined as

  • dS = δqT

  • dHT

  • dS = δqrevT

  • dS = dH - dGT


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39.

For a spontaneous process, the correct statement(s) is (are)

  • (Gsystem)T,p> 0

  • (Ssystem ) + (Ssurrounding) >0

  • (Gsystem )T,p <0

  • (Usystem)T,V>0


40.

Pressure-volume (pV) work done by an ideal gaseous system at constant volume is (where E is internal energy of the system)

  • -p/p

  • zero

  • -Vp

  • -E


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