Question

Explain the differences in S^o for the following substances

1. S^o_H2O(l)= 70.0 J/mol*K vs. S^o_H2O(g)=111.3 J/mol*K

2. S^o_ClO4-(aq)=184 K/mol*K vs. S^o_{SO3(2-) (aq)}= -29.3 J/mol*K

3. Whyi si the S^o value for SO₃^2- negative?

Answer 1

Ans. 1. Entropy of H2O(g) is more than entropy of H2O(l) because randomness of H2O molecule is more in gaseous state as in gaseous state has more volume and in liquid, volume is lower and H2O molecule has limited space to move.

Ans. 2 Entropy of ClO4- is more than SO3 2- in aqueous state becase of ClO4- is smaller in size than SO3 2- as Sulphur size is more than ClO4 - and second reason is that In SO3 2- has more negative charge and it is more attracted to water molecule through dipole dipole interaction.

Ans.3. Negative entropy of SO3 2- is due to more negative charge that can attract more of the water molecule and restrict the movement of SO3 2- in aqueous solution.