Question

Given below are two statements: one is labelled as $Assertion\left(A\right)$ and the other is labelled as $Reason\left(R\right)$.

$Assertion\left(A\right)$ : Barium carbonate is insoluble in water and is highly stable.

$Reason\left(R\right)$ : The thermal stability of the carbonates increases with increasing cationic size.

Choose the most appropriate answer from the options given below:

JEE MAIN 2021

• A. $\left(A\right)$ is true but $\left(R\right)$ is false.
• B. $\left(A\right)$ is false but $\left(R\right)$ is true.
• C. Both $\left(A\right)$ and $\left(R\right)$ are true and $\left(R\right)$ is the true explanation of $\left(A\right)$.
• D. Both $A$ and $R$ are true but $R$ is not the true explanation of $A$

Answer 1

The correct option is C Both $\left(A\right)$ and $\left(R\right)$ are true and $\left(R\right)$ is the true explanation of $\left(A\right)$.

Carbonates of alkaline earth metals are insoluble in water and can be precipitated by addition of a sodium or ammonium carbonate solution to a solution of a soluble salt of these metals. The solubility of carbonates in water decreases as the atomic
number of the metal ion increases. All the carbonates decompose on heating to give carbon dioxide and the oxide. Beryllium carbonate is unstable and can be kept only in
the atmosphere of $C{O}_2$. The thermal stability increases with increasing cationic size.