Question

On mixing 15.0 ml of ethyl alcohol of density 0.792 g ml -1 with 15 ml of pure water at 40 C, the resulting solution is found to have a density of 0.924 g ml -1. The percentage contraction in volume is :

• A. 8 %
• B. 2 %
• C. 3 %
• D. 4 %

Answer 1

Answer: (C)

3 %

Answer 2

(3)

Mass of ethyl alcohol = 1.5 ´ 0.792 g

Mass of water = 15 ´ 1

Total mass of solution = 15 + 0.792 ´ 15 = 26.88

Volume of solution$= \frac{mass}{density} = \frac{26.88}{0.924} = 29.09$

% decrease in volume S$= \left( \frac{30 = 29.09}{30} \right) \times 100 \cong 3\%.$