It is observed that Calcium on reaction with water floats on its surface. Explain why it happens. Also write a balanced chemical equation for the reaction that occurs. What happens when the aqueous solution of the product of this reaction reacts with Carbon dioxide gas? Write a balanced chemical equation for the reaction.

1. Why Calcium Floats on Water

When calcium metal reacts with water, the reaction is less violent compared to sodium or potassium. The heat evolved is not sufficient for the hydrogen gas produced to catch fire. Instead, the bubbles of hydrogen gas ($H_2$) formed stick to the surface of the calcium metal, which makes it float.

2. Balanced Chemical Equation for the Reaction

$$Ca(s) + 2H_{2}O(l) ightarrow Ca(OH)_{2}(aq) + H_{2}(g)$$

Here, the product formed is an aqueous solution of calcium hydroxide ($Ca(OH)_2$), also known as limewater.

3. Reaction of the Product with Carbon Dioxide Gas

When carbon dioxide gas ($CO_2$) is passed through the aqueous solution of calcium hydroxide, it reacts to form an insoluble white precipitate of calcium carbonate ($CaCO_3$) and water. This causes the solution to turn milky.

Balanced Chemical Equation:

$$Ca(OH)_{2}(aq) + CO_{2}(g) ightarrow CaCO_{3}(s) + H_{2}O(l)$$