Question

Zinc dissolves in hydrochloric acid to yield hydrogen gas: zn(s) + 2hcl(aq) → zncl2(aq) + h2(g) when a 12.7 g chunk of zinc dissolves in 500. ml of 1.450 m hcl, what is the concentration of hydrogen ions remaining in the final solution?

Answer 1

First calculate the initial moles of HCl.

HCl moles i = (1.45 moles / L) * 0.5 L = 0.725 moles HCl

 

Then calculate how much HCl is consumed by stoichiometry:

HCl moles consumed = (12.7 g Zn / 65.38 g / mol) * (2 moles HCl / 1 mole Zn) = 0.388 moles

 

So HCl moles left is:

HCl moles f = 0.725 – 0.388 = 0.3365 moles

For every 1 mole HCl there is 1 mole H, therefore:

H moles final = 0.3365 moles

 

So final concentration of H ions is:

Concentration H = 0.3365 moles / 0.5 L = 0.673 M