How many grams of KOH is contained in 0.5 l of a 25% solution (P = 1.24 g / ml)?

Given:
V solution (KOH) = 0.5 l = 500 ml
ω (KOH) = 25%
ρ solution (KOH) = 1.24 g / ml

To find:
m (KOH) -?

Solution:
1) Calculate the mass of the potassium hydroxide solution:
m solution (KOH) = ρ solution (KOH) * V solution (KOH) = 1.24 * 500 = 620 g;
2) Calculate the mass of potassium hydroxide in the solution:
m (KOH) = ω (KOH) * m solution (KOH) / 100% = 25% * 620/100% = 155 g.

Answer: The mass of KOH is 155 g.