If 2.5 moles of zinc react with 6.0 moles of hydrochloric acid react in the equation $Zn+2HCl\to ZnC{l}_2+H_2$ , what is the limiting reactant?

The correct option is A $Zn$
$Zn+2HCl\to ZnC{l}_2+H_2$
1 mole of Zn reacts with 2 moles of HCl.
2.5 moles of $Zn$ will react with $2\times 2.5=5.0$ moles of $HCl.$
However 6.0 moles of $HCl$ are present.
Thus, $HCl$ is the excess reactant and $Zn$ is the limiting reactant.