Question

What happens when solid \(\text{Na}_2\text{CO}_3\) dissolved in water?

• A. an increase in \([\text{OH}^-]\)
• B. no change in pH
• C. an increase in \([\text{H}^+]\) ions
• D. turns blue litmus red.

Hint:

Carbonate ion is the anion of a weak acid, so it hydrolyses and releases OH$^-$.

Answer 1

The Correct Option is A

Step 1: Think about the parent acid and base
Strong base plus weak acid always gives an alkaline salt solution.

Step 2: Test each statement
Hydroxide ions increase, so (A) is true. The pH moves above $7$, so (B) fails. H$^+$ drops, so (C) fails. Blue litmus stays blue in base, so (D) fails.

Final Answer:
Option (A). \[ \boxed{\text{(A)}} \]