Ncert Exercises & Solutions

Match the statements given in column 1 with corresponding characteristics given in column II and choose the correct option:

	Column -I		Column -II
A.	Entropy of vaporization	1.	Decreases
B.	K for a spontaneous process	2.	Is always positive
C.	Crystalline solid state	3.	Lowest entropy
D.	\(\Delta U\) in an adiabatic expansion of ideal gas	4.	\(\Delta H_{vap} \over T_b\)

Codes

Hint: Entropy of vaporization =

\frac{∆ H_{vap}}{T_{b}}

A. Entropy of vaporisation is always positive. It is equal to

\frac{∆ H_{vap}}{T_{b}}

∆_{r} G ° = - RT \ln K

If K is positive,

∆_{r} G ° =

negative and reaction is spontaneous.

C. Crystalline solid-state has the lowest entropy.

D. During the adiabatic expansion of an ideal gas, q = 0. Hence,

∆ U = q + W

gives

∆ U = W

, i.e., work done is at the cost of internal energy which decreases.