In which case is Raoult's law not applicable?

For $0.1 \ M$ solutions of the following electrolytes,the colligative property will follow the order:

Which of the following will have the lowest vapor pressure?

$19.5 \text{ g}$ of fluoroacetic acid (molar mass = $78 \text{ g mol}^{-1}$) is dissolved in $500 \text{ g}$ of water at $298 \text{ K}$. The depression in the freezing point of water was $1^\circ\text{C}$. What is $K_a$ of fluoroacetic acid? (For water, $K_f = 1.86 \text{ K kg mol}^{-1}$). Assume molarity and molality to have same values.

The freezing point of equimolal aqueous solution will be highest for

The boiling point (in ${}^{\circ}C$) of $0.1 \, molal$ aqueous solution of $CuSO_{4} \cdot 5H_{2}O$ at $1 \, bar$ is closest to $.....$
[Given : Ebullioscopic (molal boiling point elevation) constant of water,$K_{b}=0.512 \, K \, kg \, mol^{-1}$ ]