Calculate the mass of potassium hydroxide required to completely neutralize 29.9 g of hydrogen chloride.

Given:

m (HCl) = 39.9 g

To find:

m (KOH) -?

Decision:

KOH + HCl = KCl + H2O, – we solve the problem based on the composed reaction equation:

1) Find the amount of hydrogen chloride that has reacted:

n (HCl) = m: M = 29.9 g: 36.5 g / mol = 0.82 mol

2) We compose a logical expression:

If 1 mol of HCl requires 1 mol of KOH,

then 0.82 mol HCl will require x mol KOH,

then x = 0.82 mol.

3) Find the mass of alkali required for the reaction to proceed:

m (KOH) = n * M = 0.82 mol * 56 g / mol = 45.92 g.

Answer: m (KOH) = 45.92 g.