Question

K4[Fe(CN)6] is supposed to be 40% dissociated when 1 M solution prepared. its boiling point is equal to another 20% mass by volume of non-electrolytic solution A. Considering molality=molarity. the molecular weight of A is

Answer 1

On dissociating, Potassium ferrocyanide will produce four potassium ions and one ferrocyanide ion .

The equation for their dissociating process is as follows:

K4Fe ( CN) 6 - - - - - -> 4 K+   +   Fe( CN ) 6

As for forward reaction, we already know that :

Δ Tf = i Kf m

Answer 2

Answer:Molecular mass of Compound A  is 76.92 g/mol.

Explanation;

Given ,molality(m)=molarity(M)

van't Hoff factor  for $K_4[Fe(CN)_6]$ = i

$\alpha =\frac{i-1}{n-1}$

n = 5,$\alpha$ = 40 % = 0.4

i = 1.6

van't Hoff factor  for for non-electrolyte A = i'=1

$T_f$ = Boiling point of 1 M solution with $K_4[Fe(CN)_6]$

$T_f'$ = Boiling point of 20% mass by volume of non-electrolytic solution A

Mass of compound A = 20 g in 100 mL solution

$T_f=T_f'$

$\Delta T_f=\Delta T_f'$

$i\times k_f\times m=i'\times k_f\times m'$

$i\times k_f\times 1 M=i'\times k_f\frac{20 g}{M.M\times 0.1 L}$

$2.6\times 1 m=1\times \frac{20 g}{M.M\times 0.1000 L}$

M.M= 76.92 g/mol

Molecular mass of Compound A  is 76.92 g/mol.