0.5 molal aqueous solution of a weak acid ( HX ) is 20 % ionised. If K _f for water is 1.86 Kg mol ⁻¹ , the lowering in freezing point of the solution is:

Step-by-step solution

As T _f=i k_f ~m For aligned & HX H ⁺+ X ⁻ & t=0 1 0 0 & array llll t_ eq & (1-0.20) & 0.20 & 0.20 array & aligned Total no. of moles =1-0.20+0.20 aligned +0.20 & =1+0.20=1.2 T _f & =1.2 1.86 0.5 & =1.1160 aligned Related Theory The boiling point and freezing point are colligative properties. Due to the addition of solutes, the boiling point tends to increase, and freezing point tends to decrease.