MCQ
How much amount of $\mathrm{NaCl}$ should be added to $600\; \mathrm{g}$ of water $(\rho=1.00\; \mathrm{g} / \mathrm{mL})$ to decrease the freezing point of water to $-0.2^{\circ} \mathrm{C} ?$ ............. $\mathrm{gm}$

(The freezing point depression constant for water $=2\; \mathrm{K}\; \mathrm{kg} \;\mathrm{mol}^{-1}$ )

  • A
    $2.25$
  • B
    $2$
  • $1.75$
  • D
    $1.5$

Answer

Correct option: C.
$1.75$
c
$\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{i} \times \mathrm{m} \times \mathrm{K}_{\mathrm{f}}$

$0.2=2 \times 2 \times \frac{\mathrm{w} / 58.5}{600 / 1000}$

$\mathrm{w}=1.755 \mathrm{gm}$

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