What mass of potassium should be taken to prepare an aqueous solution of potassium hydroxide

What mass of potassium should be taken to prepare an aqueous solution of potassium hydroxide weighing 100 g with a mass fraction of 8%.

1. Let’s write down the reaction of obtaining potassium hydroxide:

2K + 2H2O = 2KOH + H2 ↑;

2.Calculate the mass of potassium hydroxide:

m (KOH) = w (KOH) * m (solution) = 0.08 * 100 = 8 g;

3.Calculate the chemical amounts of hydroxide and metal:

n (KOH) = m (KOH): M (KOH);

M (KOH) = 39 + 16 + 1 = 56 g / mol;

n (KOH) = 8: 56 = 0.143 mol;

n (K) = n (KOH) = 0.143 mol;

4.determine the mass of potassium:

m (K) = n (K) * M (K) = 0.143 * 39 = 5.577 g.

Answer: 5.577 g.