Verified Solution • 2025–26 Session moderate

QJEEM10Chf5da: JEE Main 2010 Chemistry - Class 12 JEEM10Chf5da Solution: If sodium sulphate is considered to be completely dissociated…

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water (∆Tf), when 0.01 mol of sodium sulphate is dissolved in 1 kg of water, is (Kf = 1.86 K kg mol–1)

Multiple Choice Options

  • A 0.0372 K
  • B 0.0558 K
  • C 0.0744 K
  • D 0.0186 K

Step-by-Step Verified Solution

Sodium sulphate dissociates as

Na2SO4(s)→2Na++SO4−−N{a_2}S{O_4}\left( s \right) \to 2N{a^ + } + SO_4^{ - - }

hence van't hoff factor i=3i=3

Now ΔTf=i kf.m=3×1.86×0.01\Delta {T_f} = i\,{k_f}.m = 3 \times 1.86 \times 0.01

=0.0558 K= 0.0558\,K

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