Question

Concentrated acid are never used for the preparation of hydrogen

Answer 1

Concentrated acids are not used in preparation of hydrogen because there may be immediate production of hydrogen which is a violent or explosive reaction and also there is excessive production of heat (exothermic reaction).


Also when you used Concentrated acids with metals to produce hydrogen, they instead react with each other to produce other compounds.

For eg. Conc sulphuric acid would react to give sulphur dioxide in larger amounts