Question

A student wants to prepare a solution of acetone and water having $30\%$ v/v. If $6mL$ of acetone has been taken then how much water must be added to get the desired concentration?
[3 Marks]

Answer 1

Given: Volume of solute (acetone) $=6mL$
Concentration (v/v) of solution $=30\%$
To find: The amount of water (in mL) required to get the desired concentration of $30\%$ v/v.

Solution:
Let the volume of water (solvent) required to be x.
So, the volume of solution $=6+x$
We know that,
Concentration of a solution (v/v%) $=\frac{Volumeofsolute}{Volumeofsolution}\times 100$
[1 Mark]

On putting the values in the formula, we get
$\Rightarrow \frac{6}{6+x}\times 100=30$
$\Rightarrow 600=180+30x$
$\Rightarrow 30x=600-180$
$\Rightarrow x=\frac{420}{30}$
$x=14mL$
[2 Marks]