Question

The zinc content of a 1.56 g ore sample was determined by dissolving the ore in HCl, which reacts with the zinc, and then neutralizing excess HCl with NaOH. The reaction of HCl with Zn is shown below.

Zn(s) + 2HCl(aq) --> ZnCl_2(aq) + H₂(g)

The ore was dissolved in 150 mL of 0.600 M HCl, and the resulting solution was diluted to a total volume of 300 mL. A 20.0 mL aliquot of the final solution required 9.46 mL of 0.540 M NaOH for the HCl present to be neutralized. What is the mass percentage (%w/w) of Zn in the ore sample?

________ % Zn

Answer 1

The question deals with back titration:

Based on the stoichiometry of the reactions:

Zn(s) + 2HCl(aq) ZnCl₂₍aq) + H₂(g)

HCl(aq) + NaOH(aq) NaCl(aq) + H₂O(l)

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