Question

how is dihydrogen obtained from:

i) water

ii)dilute acids

iii) alkalies

Answer 1

Dihydrogen means two molecules of hydrogen atoms which implies hydrogen gas.

Therefore we are seeking to find ways of forming hydrogen gas from the following :

1. WATER

Hydrogen gas is obtained from water through electrolysis whereby electric current splits water to form oxygen at the anode and hydrogen at the cathode.

2. DILUTE ACIDS

This involves the reaction of dilute acids such as HCl with metals that are above hydrogen in the reactivity series so that the hydrogen ions in the acids are displaced to form respective salt and hydrogen gas.

3.ALKALIES

Reaction of concentrated alkali with a metal with a lower reactivity series such as Aluminum to produce hydrogen gas. The reaction is exothermic.