Which is the limiting reactant in the following chemical equation? Zn + 2HCl >> 2 ZnCl2 + H2 with 10 moles of Zn and 15 moles of HCl?

Zn + 2HCl → 2ZnCl2 + H2
1 mole of Zn reacts with 2 moles of HCl.

Initial no. of moles of Zn = 10 mol
Initial no. of moles of HCl = 15 mol

When HCl is completely reacted, no. of moles Zn needed = 15 × (1/2) = 7.5 mol
There are 10 moles of Zn, but only 7.5 moles of Zn are needed.
Thus, Zn is in excess, and HCl is the limiting reactant.

HCl is the limiting reactant.
In the balanced equation.
ONE mole of Zn reacts with TWO(2) moles of HCl

So 15 moles HCl will only react with 15/2 = 7.5 moles Zn . Hence at 10 moles Zn is in excess.