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, $Mg \left( HCO _{3}\right)_{2}$ is converted to $MgCO _{3}$
Reason $R$ : The solubility product of $Mg ( OH )_{2}$ is greater than that of $MgCO _{3}$.
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, $Mg \left( HCO _{3}\right)_{2} \stackrel{\text { heating }}{\longrightarrow } Mg ( OH )_{2} \downarrow+2 CO _{2} \uparrow$ Assertion is false.

$MgCO _{3}$ 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.