Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): If the pH of a saturated solution of a sparingly soluble salt M(OH) ₂ is increased from 8 to 9 , its solubility decreases by a factor of 100 . Reason (R): For a sparingly soluble salt of type M(OH) ₂ , the solubility ( s ) is inversely proportional to the hydroxide ion concentration ( [ OH ^-] ). I

Step-by-step solution

The dissociation of M(OH) ₂ is given by: M(OH) ₂ (s) M ²⁺ (aq) + 2 OH ^- (aq) The solubility product is K_ sp = [ M ²⁺][ OH ^-]^2 . If the solubility is s , then [ M ²⁺] = s . Therefore, s = K_ sp [ OH ^-]^2 . This shows that solubility s is inversely proportional to the square of the hydroxide ion concentration ( [ OH ^-]^2 ), not just [ OH ^-] . Thus, the Reason (R) is false. When pH increases from 8 to 9 , the pOH decreases from 6 to 5 . This means [ OH ^-] increases from 10⁻⁶ M to 10⁻⁵ M , which is an increase