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Choose the correct option.
The molal freezing point constant of water is . Therefore, the freezing point of solution in water…
The molal freezing point constant of water is $1\cdot86\text{ K kg mol}^{-1}$. Therefore, the freezing point of $0\cdot1\text{ M NaCl}$ solution in water is expected to be:
- (1)$-1\cdot86^\circ\text{C}$
- (2)$-0\cdot372^\circ\text{C}$
- (3)$-0\cdot186^\circ\text{C}$
- (4)$+0\cdot372^\circ\text{C}$
Answer
Answer
AICorrect option: (2)
Answer: (2) $-0\cdot372^\circ\mathrm{C}$
NaCl dissociates into two ions ($i = 2$), so $\Delta T_f = i K_f m = 2 \times 1\cdot86 \times 0\cdot1 = 0\cdot372\ \mathrm{K}$ and the freezing point is $-0\cdot372^\circ\mathrm{C}$.
From ISC 2018 Specimen Chemistry Paper 1, question 1(b)(i).