Q.

Following limiting molar conductivities are given as:  

λm(H2SO4)∘=x S cm2 mol-1

λm(K2SO4)∘=y S cm2 mol-1

λm(CH3COOK)∘=z S cm2 mol-1

λm∘ (in S cm2 mol-1) for CH3COOH will be                   [2019]

1 x-y+2z  
2 x+y-z  
3 x-y+z  
4 (x-y)2+z  

Ans.

(4)

According to Kohlrausch's law,  

Λmo for CH3COOH =λCH3COO-∘+λH+∘

Λ° for H2SO4 =2λH+∘+λSO42-∘=x S cm2 mol-1             ...(i)

Λ° for K2SO4 =2λK+∘+λSO42-∘=y S cm2 mol-1             ...(ii)

Λ° for CH3COOK =λCH3COO-∘+λK+∘=z S cm2 mol-1        ...(iii)

On adding equation (i) and 2×(iii) and subtracting (ii), we get  

2λH+∘+λSO42-∘ +2λCH3COO-∘ +2λK+∘ -2λK+∘ -λSO42-∘ =x+2z-y

2λH+∘+2λCH3COO-∘=x+2z-y

λH+∘+λCH3COO-∘ =(x-y)2+z