alleryFreezing point depression: ΔT_f = K_f × m. For 0.5 molal NaCl (assume full dissociation, K_f = 1.86), the depression is:
A0.46 K
B0.93 K
C3.72 K
D1.86 K
Answer & Solution
Correct answer: D. 1.86 K
NaCl dissociates into 2 ions (i = 2 van't Hoff factor).
ΔT_f = i × K_f × m = 2 × 1.86 × 0.5 = 1.86 K. So 0.5 m NaCl freezes at -1.86°C.
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