Zinc and hydrochloric acid react according to the reaction:
`Zn_((s))+2HCl_((aq.))rarr ZnCl_(2(aq.))+H_(2(g))`
If `0.30` mole of `Zn` are added to hydrochloric acid containing `0.52` mole `HCl`, how many moles of `H_(2)` are produced?

Explanation

The balanced chemical equation for the reaction is :
`underset("1 mol")(Zn(s))+underset("2 mol")(2HCl(aq))rarrZnCl_(2)(aq)+underset("1 mol")(H_(2)(g))`
Step I. Determine of limiting reactant
1 mole of Zn react with HCl = 2 mol
0.30 mole of Zn react with HCl `= 2 xx 0.3 = 0.6 mol`
But HCl actually present in solution `= 0.52` mol
This means that HCl is present in lesser amount than what is actually required.
`:.` It is the limiting reactant
Step II. Determination of moles hydrogen produced
2.0 mole of HCl on reacting with Zn produce `H_(2)(g)=1` mol
0.52 mole of HCl on reacting with Zn produce `H_(2)(g)=(1xx 0.52)/(2)=0.26` mol.