Calculate the mass of a 28.0 wt% KOH solution required to make 800.0 mL of 0.436 M KOH.

70.0 g

Explanation:

We want to make 800.0 mL of 0.436 M KOH. The moles of KOH required are:

0.8000 L * 0.436 mol/L = 0.349 mol

The molar mass of KOH is 56.11 g/mol. The mass corresponding to 0.349 moles is:

0.349 mol * 56.11 g/mol = 19.6 g

The starting solution has a concentration of 28.0 wt% KOH, that is, there are 28 g of KOH per 100 grams of solution. The mass of solution that contains 19.6 g of KOH is:

19.6 g KOH * (100 g solution/28.0 g KOH) = 70.0 g solution