What mass of zinc chloride is formed when 3.269 g of zinc reacts with excess hydrochloric acid? (Hint: first write a balanced chemical equation for the reaction).

Question

I know the balanced equation is : Zn(s) + 2HCl (aq) -------> ZnCl2 (aq) + H2(g). What do I do after? The question is 3 marks.

Answer 1

Zn(s) + 2HCl (aq) -------> ZnCl₂ (aq) + H₂(g) ... balanced equation (you got that part correct).

Next, we find the moles of Zn present:

3.269 g Zn x 1 mol Zn / 65.39 g Zn = 0.04999 moles Zn

Next we use the stoichiometry (mole ratios) of the balanced equation to find the moles of ZnCl₂ that will be formed from this many moles of Zn:

0.04999 mols Zn x 1 mol ZnCl₂ / mol Zn = 0.04999 moles ZnCl₂

Finally, we simply use the molar mass of ZnCl₂ to convert moles to grams:

0.04999 mols ZnCl₂ x 136.29 g /mol = 6.813 g ZnCl₂ (4 sig. figs.)