Question

What is the quantity of water that should be added to 16 g. methanol to make the mole fraction of methanol as 0.25 :

• A. 27 g.
• B. 12 g.
• C. 18 g.
• D. 36 g.

Answer 1

Answer: (A)

27 g.

Answer 2

(1)

Let wg water in added to 16 g CH3OH

molality $= \frac{16 \times 1000}{W \times 32} = \frac{500}{W}$

$\frac{500}{W} = \frac{x_{A} \times 1000}{\left( 1 - x_{A} \right)m_{B}} = \frac{0.25 \times 1000}{0.75 \times 18}W = 27gm$.