Solutions Question 365

Question: If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water $ ( \Delta T_{f} ), $ when 0.01 mol of sodium sulphate is dissolved in 1 kg of water, is $ ( K_{f}=1.86Kkgmo{l^{-1}} ) $

Options:

A) 0.372 K

B) 0.0558 K

C) 0.0744 K

D) 0.0186 K

Show Answer

Answer:

Correct Answer: B

Solution:

Sodium sulphate dissociates as $ Na_2SO_4( s )\xrightarrow{{}}2N{a^{+}}+SO_4^{-} $ hence van’t hoff factor i = 3 Now $ \Delta T_{f}=ik_{f}.m $

$ =3\times 1.86\times 0.01=0.0558K $



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