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Thermodynamics · Question 71

AIPMT 2002MCQMedium📈 Topic in 12% papers+4−1
1

Heat of combustion Ho for C(s), H2(g) and CH4(g) are -94, -68 and -213 kcal/mol, then Ho for C(s) + 2H2(g) CH4(g) is

  1. -17 kcal
  2. -111 kcal
  3. -170 kcal
  4. -85 kcal

Answer

(1) -17 kcal

Solution

For a reaction, Ho = c Ho(reactants) - c Ho(products)

⇒ Ho = [ c Ho(C) + 2 c Ho(H2)] - c Ho(CH4)

⇒ Ho = [-94 + 2(-68)] - (-213)

= -230 + 213

∴ Ho = -17 kcal

Answer: (1)

AIPMT 2002

Keep practising — Thermodynamics

2

2 moles of an ideal gas at 27 temperature is expanded reversibly from 2 lit. to 20 lit. Find entropy change. (R = 2 cal/mol K)

  1. 92.1
  2. 0
  3. 4
  4. 9.2
AIPMT 2002
3

Change in enthalpy for reaction, 2H2O2(l) 2H2O(l) + O2(g) if heat of formation of H2O2(l) and H2O(l) are -188 and -286 kJ/mol respectively, is

  1. -196 kJ/mol
  2. +196 kJ/mol
  3. +948 kJ/mol
  4. -948 kJ/mol
AIPMT 2001
4

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

  1. q = w = 500 J, E = 0
  2. q = E = 500 J, w = 0
  3. q = -w = 500 J, E = 0
  4. E = 0, q = w = -500 J
AIPMT 2001
5

Enthalpy of CH4 + 12O2 CH3OH is negative. If enthalpy of combustion of CH4 and CH3OH are x and y respectively. Then which relation is correct?

  1. x > y
  2. x < y
  3. x = y
  4. x ≥ y
AIPMT 2001
6

2Zn + O2 2ZnO; = -616 J 2Zn + S2 2ZnS; = -293 J S2 + 2O2 2SO2; = -408 J for the following reaction 2ZnS + 3O2 2ZnO + 2SO2 is

  1. -731 J
  2. -1317 J
  3. -501 J
  4. +731 J
AIPMT 2000
7

The entropy change in the fusion of one mole of a solid melting at 27 (latent heat of fusion is 2930 J mol-1) is :

  1. 9.77 J/mol-K
  2. 10.77 J/mol-K
  3. 9.07 J/mol-K
  4. 0.977 J/mol-K
AIPMT 2000
8

For the reaction, C2H5OH(l) + 3O2(g) 2CO2(g) + 3H2O(l) which one is true

  1. = - RT
  2. = + RT
  3. = + 2RT
  4. = - 2RT
AIPMT 2000

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