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 5.00 x 102 ml of 1.450 m hcl, what is the concentration of hydrogen ions remaining in the final solution? 0 m0.388 m0.674 m0.776 m1.06 m

Explanation:

We are given the amounts of two reactants, so this is a limiting reactant problem.

1. Data:

We know we will need an equation with masses and molar masses, so let’s gather all the information in one place.  

M_r:            65.38

                     Zn   +   2HCl ⟶ ZnCl₂ + H₂

m/g:             12.7

V/mL:                      5.00×10²

c/mol·L⁻¹:                  1.450

2. Moles of each reactant  

(a) Moles of Zn

(b) Moles of HCl

V = 5.0× 10² mL = 0.5000 L

3. Identify the limiting reactant

Calculate the moles of ZnCl₂ obtained from each reactant

(i) From Zn

The molar ratio is 1 mol ZnCl₂:1 mol Zn

(ii) From HCl

The molar ratio is 1 mol ZnCl₂:2 mol HCl

Zinc is the limiting reactant, because it produces fewer moles of ZnCl₂.

4. Moles of HCl reacted

The molar ratio is 2 mol HCl:1 mol Zn

5. Moles of HCl remaining

n = 0.7250 - 0.3885 = 0.3365 mol HCl

6. Concentration of hydrogen ions

The HCl is completely dissociated.