Question

How many grams of a 25% by mass solution of KOH to be added to 400 ml of water to prepare a 15% by mass solution?

Answer 1

Let x gm of 25% solution is added to 400 gm of water (density of water = 1 g/mL).
Then according to the question,
$\frac{0.25x}{x+400}=0.15$
$\Rightarrow x=600$ gm