Question

The sparkling red colour seen in firecrackers after they burst is due to the presence of:
(A) sulphur
(B) sodium
(C) strontium
(D) magnesium

Answer 1

Hint: Think about the chemical composition of firecrackers and consider all the metallic compounds that are used to impart colour to the fireworks.

Complete step by step solution:
First, let us look at all the components of fireworks and how they work before moving on to the chemicals that impart colour to the fireworks.
Fireworks are made up of four components viz. the oxidizers, the fuel, the colouring agents and the binders.
- The oxidizers release the oxygen that is required for the burning. It is usually put in the fireworks in the form of perchlorate ions.
- The fuel is either gunpowder or just plain charcoal, this is the substance that burns and produces light and is the heart of all fireworks.
- The binders are paste-like substances like dextrin, which keep all the chemical components of the fireworks together.
Now, onto the colouring agents, various metal oxides are used to impart colour to the fireworks when they burst. Some chemical compounds that are used as colouring agents are:
- Strontium carbonate ($SrC{{O}_{3}}$): for red fireworks
- Calcium chloride ($CaC{{l}_{2}}$): for orange fireworks
- Sodium nitrate ($NaN{{O}_{3}}$): for yellow fireworks
- Barium chloride ($BaC{{l}_{2}}$): for green fireworks
- Copper chloride ($CuCl$): for blue fireworks
From this information, we can say that strontium carbonate is used to impart a sparkling red colour to the fireworks.

Hence, the correct answer to this question is ‘C. strontium’

Note: Sometimes instead of dextrin, the binder ‘paron’ is used to enhance the colour of red and green fireworks. For red coloured fireworks, sometimes lithium carbonate is also used instead of strontium carbonate. So, do not get confused if lithium is present in the options instead of strontium.