Question

Choose the correct statement from the following :

• A. The standard enthalpy of formation for alkali metal bromides becomes less negative on descending the group.
• B. The low solubility of CsI in water is due to its high lattice enthalpy.
• C. Among the alkali metal halides, LiF is least soluble in water.
• D. LiF has least negative standard enthalpy of formation among alkali metal fluorides.

Answer 1

Answer: (C)

1. Standard enthalpy of formation for alkali metal bromides becomes more negative on desending down the group.
2. In case of $CsI$, lattice energy is less, but $Cs ^{+}$is having less hydration enthalpy due to which it is less soluble in water.
3. For alkali metal fluorides, the solubility in water increases from lithium to caesium. $LiF$ is least soluble in water.
4. Standard enthalpy of formation for $LiF$ is most negative among alkali metal fluorides.