Question

On mixing $15.0$ ml of ethyl alcohol of density $0.792$g $m{l}^{-3}$ with $15$ml of pure water at $4^o$C, the resulting solution is found to have a density of $0.924$g $m{l}^{-1}$. The percentage contraction in volume is:

• A. $8\%$
• B. $2\%$
• C. $3\%$
• D. $4\%$

Answer 1

Answer: (C)

$3\%$

On mixing$15mL$ of pure water and $15mL$of ethyl alcohol, the ideal solution become$30mL$.

$15mL$ of etyl alcohol haing a density of $0.792g/mL$ weighs $11.8g$. $15mL$ of pure water at $4^{0}C$ has a density of $1.0g/mL$ and weighs $15g$.

So the mass of solution is $26.88g$.

The density of the solution is given to be $0.924g/mL$. So its volume is about $29.09mL$.

$Percentagecontraction=$($ideal$ $volume$) -$($$observed$ $volume$ )$\times 100$$/ideal$ $volume$.

$=30\times 29.9\times 100/30$

$=3.03$

or $3$%