Question

When hydrogen burns in oxygen, water is formed; when electricity is passed through water, hydrogen and oxygen are given out. Name the type of chemical change involved in the two cases.

Answer 1

When Hydrogen burns in Oxygen, water is formed from the combination of Hydrogen and water, this type of reaction is called a combination reaction.

$\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}⟶\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{liq}\right)}$

When electricity is passed through water, hydrogen, and oxygen gases are given out, the chemical changes involved here are decomposition and the type of reaction is a decomposition reaction.

${\mathrm{H}}_2\mathrm{O}\left(\mathrm{liq}\right)\stackrel{\mathrm{Electric}\mathrm{current}}{\to }{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$

Hence, the answer will be a combination reaction and decomposition reaction.