$0.5$ molal aqueous solution of a weak acid $(HX)$ is $20\%$ ionised. If $K_f$ for water is $1.86\, K\, kg\, mol^{-1}$,the lowering in freezing point of the solution is $........ K$.

Consider the following solutions:
$I$. $1 \ M$ glucose $(aq.)$
$II$. $1 \ M$ sodium chloride $(aq.)$
$III$. $1 \ M$ acetic acid in benzene
$IV$. $1 \ M$ ammonium phosphate $(aq.)$

Which one of the following $0.10 \ M$ aqueous solutions will exhibit the largest freezing point depression?

The observed osmotic pressure for a $0.10 \ M$ solution of $Fe(NH_4)_2(SO_4)_2$ at $25 \ ^oC$ is $10.8 \ atm$. The expected and experimental (observed) values of van't Hoff factor $(i)$ will be respectively: $(R = 0.082 \ L \ atm \ K^{-1} \ mol^{-1})$

$A$ $0.0020 \ m$ aqueous solution of an ionic compound $[Co(NH_3)_5(NO_2)]Cl$ freezes at $-0.00732 \ ^oC.$ Number of moles of ions which $1 \ mol$ of ionic compound produces on being dissolved in water will be
$(K_f = 1.86 \ ^oC/m)$

$A$ $0.2 \ m$ solution of acid $HX$ is $20\%$ ionized in the solution. Given $K_f = 1.86 \ K \ kg \ mol^{-1}$,the freezing point of the solution is ........... $^oC$.