Question

Which of the following salts would have the greatest effect on the freezing point of a solution if 0.10 mole of the salt was dissolved in enough water to make 100.0 mL of solution?

• A. $NaCl$
• B. $KCl$
• C. $CaC{l}_2$
• D. $MgC{l}_2$
• E. $AlC{l}_3$

Answer 1

The correct option is E $AlC{l}_3$

$AlC{l}_3$ would have the greatest effect on the freezing point of a solution if 0.10 mole of the salt was dissolved in enough water to make 100.0 mL of solution. $AlC{l}_3$ has vant Hoff factor '4'. 1 molecule of $AlC{l}_3$ dissociates to give 4 ions. $AlC{l}_3\to A{l}^{3+}+3C{l}^{-}$

NaCl and KCl have vant Hoff factor '2'. $CaC{l}_2$ and $MgC{l}_2$ have vant Hoff factor '3'. When different solutes have same concentration, the depression in the freezing point is maximum for a solute having maximum value of vant Hoff factor.