Question
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Answer

When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide:

$\text{CaCO}_3 \xrightarrow{\ \ \ \ \ \ \ \Delta\ \ \ \ \ \ \ \ \ \ }\ \ \ \text{CaO}\ \ \ \ +\ \ \ \text{CO}_2\\ \text{Calcium}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\\text{Carbonate}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ $

When electric current is passed through acidified water, it decomposes to give hydrogen gas and oxygen gas. This reaction can be represented as:

$2\text{H}_2\text{O}\ (\text{l})\ \ \ \xrightarrow{\text{Electricity}}\ \ \ 2\text{H}_2\ (\text{g})+\text{O}_2(\text{g})$

When silver chloride is exposed to light, it decomposes to from silver metal and chlorine gas:

$2\text{AgCl}\text{(s)}\ \ \ \ \xrightarrow{\text{Light}}\ \ \ 2\text{Ag}\ (\text{s})+\ \text{Cl}_2(\text{g})$

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