Determine the percent sodium by mass in the original mixture.

Question

Zinc and sodium metal each react with sulfuric acid according to the following equations. Zn(s)+H2SO4(aq)⟶ZnSO4(aq)+H2(g)

2Na(s)+H2SO4(aq)⟶Na2SO4(aq)+H2(g)

A 26.16 g mixture of zinc and sodium is reacted with a stoichiometric amount of sulfuric acid. The reaction mixture is then reacted with 304 mL of 1.65 M barium chloride to produce the maximum possible amount of barium sulfate. Determine the percent sodium by mass in the original mixture.

mass percent Na=

If 94.27 mL of sulfuric acid was added, what was the concentration of the sulfuric acid?

Answer 1

Hi Sarah!

Summarizing the video I posted:

We need to relate the Na and Zn metal to BaSO₄. From the given chemical equations, we know that Zn produces ZnSO₄ in a 1:1 mole ratio and Na produces Na₂SO₄ in a 2:1 ratio. We then show that ZnSO₄ reacts with BaCl₂ to make BaSO₄ and Na₂SO₄ also reacts with BaCl₂ to make BaSO₄. BaCl₂ and BaSO₄ are related in a 1:1 ratio, and we are told we want to maximize BaSO₄. Thus we will make 0.5016 moles of BaSO₄.

We set up the following system of equations, where Z = moles of Zn and N = moles of Na. One equation relates atomic masses with the original mixture mass, and the other relates the molar amounts.

65.38Z + 22.99N = 26.16

1Z + 0.5N = 0.5016.

We solve for N to get moles of Na, and then convert this to grams and find the mass %!