Calculate the mass of a 10% sodium hydroxide solution required to completely neutralize a solution

Calculate the mass of a 10% sodium hydroxide solution required to completely neutralize a solution containing 4.9 grams of sulfuric acid.

Given:

m (H2SO4) = 4.9 g

w% (NaOH) = 10%

Find:

m (NaOH) -?

Solution:

2NaOH + H2SO4 = Na2SO4 + 2H2O, – we solve the problem, relying on the composed reaction equation:

1) Find the amount of sulfuric acid that has reacted:

n (H2SO4) = m: M = 4.9 g: 98 g / mol = 0.05 mol

2) We compose a logical expression:

If 1 mol H2SO4 requires 2 mol NaOH,

then 0.05 mol H2SO4 will require x mol NaOH,

then x = 0.1 mol.

3) Find the mass of the alkali solution:

m (NaOH solution) = n * M = 0.1 mol * 40 g / mol = 4 g.

4) Find the mass of alkali in the solution:

m (NaOH) = 4 g * 0.1 = 0.4 g.

Answer: m (NaOH) = 0.4 g.