Chemistry question

Question

3. Suppose in the lab, 3.68 g of zinc was allowed to react with hydrochloric acid to produce zinc chloride and hydrogen gas. How much zinc chloride should you get? Suppose that you actually recovered 7.12 g of zinc chloride. What is your per cent yield?

Answer 1

First, write the balanced equation for the reaction taking place:

Zn(s) + 2HCl(aq) ==> ZnCl₂(aq) + H₂(g) ... balanced equation

moles Zn used = 3.68 g Zn x 1 mol Zn/65.39 g = 0.05627 moles Zn

moles ZnCl₂ expected (theoretical) = 0.05627 mol Zn x 1 mol ZnCl₂/mol Zn = 0.05627 mol ZnCl₂

mass ZnCl₂ (theoretical) = 0.05627 moles x 136.29 g/mol = 7.67 g ZnCl₂ theoretical yield

Percent yield = actual yield/theoretical yield (x100%) = 7.12 g/7.67 g (x100%) = 92.8% yield