To get a 12% of v/v% of alcohol solution, how much water (in mL) should be mixed with 12 mL of alcohol?

The correct option is C 88 mL
Given,
Volume of solute (alcohol) = 12 mL
Let the volume of water (solvent) required be x mL.
So the volume of solution = (12 + x) mL
We know that,
Volume by volume percentage of solution (v/v%) $=\frac{\text{Volume of solute}}{\text{Volume of solution}}\times 100$

$\Rightarrow 12=\frac{\text{12}}{\text{12 + x}}\times 100$

⇒ 1200 = 12(12+x)
⇒ 1200 = 144 + 12x
⇒ 12x = 1200 - 144 = 1056
⇒ x = 1056/12 = 88

Therefore, 88 mL of water should be mixed with 12 mL of alcohol to make a 12% of v/v% solution.