Question

Which of the following statements is correct :

• A. Hydration energy of alkali metal ions increases down the group
• B. Caesium and Potassium are used in photoelectric cell.
• C. $Li$ does not form nitride on burning in air
• D. except $L{i}_{2}C{O}_3$ all the carbonates of alkali metals decompose on heating

Answer 1

The correct option is B Caesium and Potassium are used in photoelectric cell.

(1) Hydration energy of decreases down the group as the size of the ion increases
(2) Caesium and potassium are used as electrode in photoelectric cells because they are more electropositive i.e., small amount of light energy is required to remove the outer shell electron from them.
(3) Lithium show exceptional behaviour in reacting directly with nitrogen of air to form the nitride, $L{i}_{3}N$.
(4) $L{i}_{2}C{O}_3$ decompose on heating to form $L{i}_{2}O$ and $C{O}_2$