`0.04007 mol es H_2 * (2.016 grams H_2)/(1 mol e H_2)`, `= 0.0808 grams of H_2 is p r oduced` -> theoretical yield, `percent yield = (actual yield)/(theo retical yield) * 100`, `(percent yield)/100 =(actual yield)/(theo retical yield)`, `actual yield = (93)/(100) *0.0808 grams`. Copper is less reactive when compared to Hydrogen and hence cannot displace it. Since the zinc is oxidized and the reaction needs to remain balanced, the hydrogen atoms are reduced. It is easily oxidized by hydrogen.