Question

Rahul took 25 ml of sea water in a beaker and added one spoon of sodium carbonate to it. Which of the following will he observe?

• A. Precipitate is formed
• B. Bubbles are formed
• C. Solution colour changes to red
• D. Solution colour changes to blue

Answer 1

The correct option is A Precipitate is formed

Sea water is basically hard water. It contains dissolved salts of calcium ions, $\left({\text{Ca}}^{2+}\right)$ or magnesium ions $\left({\text{Mg}}^{2+}\right)$.
Hard water on reaction with sodium carbonate $\left({\text{Na}}_2{\text{CO}}_3\right)$ forms calcium carbonate or magnesium carbonate precipitate. This precipitate can be filtered out and soft water is obtained.