Question

powdered zinc react more vigorously with HCl than chunks of zinc?

Answer 1

This happens because particles of zinc powder being small come easily in contact with HCl .
As the particles become fine more part of zinc metal comes in contact with HCl and react vigorously.

Answer 2

Answer: Because of large surface area of powdered zinc than chunks of Zinc

Explanation:

$Zn+2HCl\rightarrow ZnCl_2+H_2$

Rate of the reaction is dependent on the concentration of reactants and the surface area of reactants.

If the reactant molecules are present in powdered form, more of it can participate in the chemical reaction as more surface of molecules is available for reaction.

Hence, powdering the zinc enhances the available surface are and thus increases the rate of reaction.