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Answer the following.
Calculate the mass of ascorbic acid (molecular mass ) to be dissolved in of acetic acid to lower…
Calculate the mass of ascorbic acid (molecular mass $= 176\text{ g mol}^{-1}$) to be dissolved in $75\text{ g}$ of acetic acid to lower its freezing point by $1\cdot5^\circ\text{C}$. Assume that the solute neither associates nor dissociates in solution.
($K_f$ for acetic acid $= 3\cdot9\text{ K kg mol}^{-1}$)
Answer
Answer
AIFormula:
$\Delta T_f = \frac{K_f \times w_2 \times 1000}{M_2 \times w_1}$
$w_2 = \frac{\Delta T_f \times M_2 \times w_1}{K_f \times 1000}$
Substitution:
$w_2 = \frac{1\cdot5\text{ K} \times 176\text{ g mol}^{-1} \times 75\text{ g}}{3\cdot9\text{ K kg mol}^{-1} \times 1000\text{ g kg}^{-1}}$
$= \frac{19,800}{3900} = 5\cdot08\text{ g}$
Final answer: 5.08 g
From ISC 2026 Chemistry Paper 1, question 19(i).
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