Question

Among the statements (a)-(d), the correct ones are :
a) Lithium has the highest hydration enthalpy among the alkali metals.
b) Lithium chloride is insoluble in pyridine.
c) Lithium cannot form ethynide upon its reaction with ethyne.
d) Both lithium and magnesium react slowly with $H_{2}O$.

• A. (a), (b) and (d) only
• B. (b) and (c) only
• C. (a), (c) and (d) only
• D. (a) and (d) only

Answer 1

The correct option is C (a), (c) and (d) only

Only $LiCl$ amongst the first group chlorides dissolve in pyridine because the solvation energy of lithium is higher than the other salts of the same group.
Lithium does not react with ethyne to form ethynilide due to its small size and high polarizability.
Lithium and Magnesium both have very small sizes and very high ionization potentials so, they react slowly with water.
Amongst all the alkali metals, $Li$ has the smallest size hence, the hydration energy for $Li$ is maximum.