Question

If 0.5 mole of zn is added to hydrochloric acid containing 0.6 mol of hcl, which reactant is in excess

Answer 1

The balanced equation for the reaction is as follows;
Zn + 2HCl --> ZnCl₂ + H₂
stoichiometry of Zn to HCl is 1:2
limiting reagent is the reactant that is fully consumed in the reaction.
the amount of product formed depends on amount of limiting reactant present.
The excess reactant is when it has been provided in excess and only a fraction of the provided amount is used up in the reaction.
Amount of Zn moles - 0.5 mol
Amount of HCl moles - 0.6 mol
If Zn is provided, number of HCl moles reacted - 0.5 x 2 = 1.0 mol of HCl is required, but only 0.6 mol of HCl is provided.
HCl is therefore the limiting reactant, 
Number of Zn moles required - 0.6 mol /2 = 0.3 mol
But 0.5 mol are given, therefore 0.2 mol of Zn is in excess