Question

Why we don't use concentrated h2so4 with zinc to produce dihydrogen?

Answer 1

Pure zinc is not used for the preparation of hydrogen gas because it is non-porous. As a result, the reaction carried out with pure zincwould be too slow. Hence impurities like copper is often added to the zinc. Copper acts as a catalyst ( by providing a large surface area) and increases the speed of the reaction.

Answer 2

your answer

we don't use concentrate h2so4 with zinc as a gas so2 or sulphur sulphur dioxide is formed
which makes the reaction not to go right

zn+h2so4------> znso4 +so2+ h2o

hope helps