Question

Explain the following reaction with the help of a balanced chemical equation:
Calcium reacts with water.

Answer 1

Hint: Calcium will react with water in a way that it will release hydrogen gas as one of its products. Calcium will also make a salt which is not soluble in water so that it will make the water hazy at the end of the reaction.

Complete step by step solution:
We know that calcium is a group-2 metal or an alkaline earth metal. We know that alkaline earth metal does not react vigorously with water as alkali metals do.
- When we allow the metallic calcium to react with water, it reacts slowly to form hydrogen gas and calcium hydroxide. So, we can write the reaction equation below.
\[C{{a}_{(s)}}+{{H}_{2}}O\to Ca{{(OH)}_{2}}+{{H}_{2}}\]
But here, we can see that the reaction is not balanced. So, we will need to balance the reaction in a way that the number of every atom is the same on both the right and left-hand side of the reaction.
- So, we will multiply ${{H}_{2}}O$ by 2. That in result will make the reaction balanced. So, a balanced reaction can be written as
\[C{{a}_{(s)}}+2{{H}_{2}}{{O}_{(l)}}\to Ca{{(OH)}_{2(s)}}+{{H}_{2(g)}}\]
- As we dip the calcium metal into water, slowly it will start reacting and simultaneously it will make the water hazy due to the formation of calcium hydroxide and hydrogen gas will also be evolved during the reaction.
- This reaction is an exothermic reaction, so that heat is evolved during the reaction. So, we can say that the enthalpy of this reaction will be negative.

Note: Remember that calcium will not make calcium hydride by its reaction of water because hydroxide is a negatively charged ion of water and it will have an affinity towards the electropositive calcium metal. So, we will get hydroxide as a product.