When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0oC and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed, The amount of heat released from this combustion in kJ ($$\Delta $$Hcomb. (CH4) = 890 kJ mol$$-$$1, $$\Delta $$Hcomb. (C3H8) = 2220 kJ mol$$-$$1) is
A reaction having equal energies of activation for forward and reverse reactions has
A
$$\Delta $$H = 0
B
$$\Delta $$H = $$\Delta $$G = $$\Delta $$S = 0
C
$$\Delta $$S = 0
D
$$\Delta $$G = 0
Explanation
For a general reaction,
ΔH = Activation energy of forward reaction –
Activation energy of backward reaction.
As, both
the energies of activation have same value thus, ΔH
= 0.
$$\Delta $$G is not equal to zero because if it is so the
reaction must be in equilibrium which is not in this
case
3
MCQ (Single Correct Answer)
AIPMT 2012 Prelims
The enthalpy of fusion of water is 1.435 kcal/mol. The molar entropy change for the melting of ice at 0oC is
A
10.52 cal/(mol K)
B
21.04 cal/(mol K)
C
5.260 cal/(mol K)
D
0.526 cal/(mol K)
Explanation
H2O($$l$$) → H2O(s)
∆H = 1.435 Kcal/mol
T = 0 + 273K = 273K
$$\Delta S = {{\Delta H} \over T}$$
$$ \Rightarrow $$ $$\Delta S = {{1.435} \over {273}}$$ = 5.26 $$ \times $$ 10-3 kcal/mol K
$$ \Rightarrow $$ $$\Delta S$$ = 5.260 cal/mol K
4
MCQ (Single Correct Answer)
AIPMT 2012 Prelims
Standard enthalpy of vaporisation $$\Delta $$vapHo for water at 100oC is 40.66 kJ mol$$-$$1. The internal energy of vaporisation of water at 100oC (in kJ mol$$-$$1) is