If 0.1 molal aqueous solution of sodium bromide freezes at -0.3348°C at one atmospheric pressure, the per cent dissociation of salt in the solution is ( = 1.86)

Question

If 0.1 molal aqueous solution of sodium bromide freezes at -0.3348°C at one atmospheric pressure, the per cent dissociation of salt in the solution is ($K_f$ = 1.86)

Prashant Kotian · Accepted Answer

Correct answer: B. Observed ΔT_f = 0.3348°C. i = ΔT_f / ( * m) = 0.3348 / (1.86 * 0.1) = 1.80. NaBr dissociates into 2 ions (n=2). i = 1 + (2-1)α => 1.80 = 1 + α => α = 0.80. Percentage dissociation = 80%.

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