Question

Given below are two statements: One is labelled as Assertion A and the other labelled as reason $R$
Assertion $A$ : During the boiling of water having temporary hardness, $Mg{\left(HC{O}_3\right)}_2$ is converted to $MgC{O}_3$
Reason $R$ : The solubility product of $Mg(OH{)}_2$ is greater than that of $MgC{O}_3$.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both A and R are true but R is not the correct explanation of A
• B. A is true but R is false
• C. Both A and R are true and R is the correct explanation of A
• D. A is false but R is true

Answer 1

Answer: (D)

For temporary hardness, $Mg{\left(HC{O}_3\right)}_2\stackrel{\text{ heating }}{⟶}Mg(OH{)}_2\downarrow +2C{O}_2\uparrow$ Assertion is false.

$MgC{O}_3$ has high solubility product than $Mg(OH{)}_2$

According to data of NCERT table $7.9$ (Equilibrium chapter), the solubility product of magnesium carbonate is $3.5\times 10^{-8}$ and solubility product of $Mg(OH{)}_2$ is $1.8\times 10^{-11}$. Hence Reason is incorrect.

The question should be Bonus.