Which of the following statements is correct for the spontaneous adsorption of a gas?
A
$$\Delta $$S is negative and, therefore $$\Delta $$H should be highly positive.
B
$$\Delta $$S is negative and therefore, $$\Delta $$H should be highly negative.
C
$$\Delta $$S is positive and therefore, $$\Delta $$H should be negative .
D
$$\Delta $$S is positive and therefore, $$\Delta $$H should also be highly positive.
Explanation
Using Gibb's-Helmholtz equation,
$$\Delta G = \Delta H - T\Delta S$$
During adsorption of a gas, entropy decreases i.e, $$\Delta $$S < 0
For spontaneous adsorption, $$\Delta $$G should be negative, which is possible when $$\Delta $$H is highly negative.
3
MCQ (Single Correct Answer)
NEET 2013 (Karnataka)
Three thermochemical equations are given below
(i) C(graphite) + O2(g) $$ \to $$ CO2(g); $$\Delta $$rHo = x kJ mol$$-$$1 (ii) C(graphite) + $${1 \over 2}$$O2(g) $$ \to $$ CO(g); $$\Delta $$rHo = y kJ mol$$-$$1 (iii) CO(g) + $${1 \over 2}$$O2(g) $$ \to $$ CO2(g); $$\Delta $$rHo = z kJ mol$$-$$1 Based on the above equations, find out which of the relationship given below is correct.
A
z = x + y
B
x = y + z
C
y = 2z $$-$$ x
D
x = y $$-$$ z
Explanation
According to Hess's law, equation (i) is equal to equations (ii) + (iii)
4
MCQ (Single Correct Answer)
NEET 2013 (Karnataka)
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