Answer these questions selecting the appropriate option given below:
Assertion : On reacting with water, calcium starts floating over water.
Reason: Calcium reacts with cold water at room temperature.
Answer & explanation
Correct answer: option 2
The correct answer is option 2. Both A and R are true but R is not the correct explanation of A.
When calcium reacts with water, it produces calcium hydroxide and hydrogen gas. Calcium is an alkaline earth metal with an atomic number of 20. This response is quite slow. The whole response is:
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
The heat that is emitted in this instance is incredibly low and insufficient to ignite the hydrogen that is formed. Instead, the calcium begins to float because the hydrogen gas bubbles that are created stick to the water's surface. Therefore, the claim is accurate.