Q18 / 150 · MHT CET 2026 (11 April Shift 1) · Chemistry
What happens when solid $\text{Na}_2\text{CO}_3$ dissolved in water?
- Correct answerAan increase in $[\text{OH}^-]$
- Bno change in pH
- Can increase in $[\text{H}^+]$ ions
- Dturns blue litmus red.
Solution
$\text{Na}_2\text{CO}_3$ is a salt of a strong base ($\text{NaOH}$) and a weak acid ($\text{H}_2\text{CO}_3$).
When dissolved in water, it dissociates completely into $\text{Na}^+$ and $\text{CO}_3^{2-}$ ions.
The carbonate ion undergoes anionic hydrolysis:
$\text{CO}_3^{2-} + \text{H}_2\text{O} \rightleftharpoons \text{HCO}_3^- + \text{OH}^-$
This hydrolysis produces $\text{OH}^-$ ions, leading to an increase in $[\text{OH}^-]$ concentration and making the solution basic.
Answer: an increase in $[\text{OH}^-]$
When dissolved in water, it dissociates completely into $\text{Na}^+$ and $\text{CO}_3^{2-}$ ions.
The carbonate ion undergoes anionic hydrolysis:
$\text{CO}_3^{2-} + \text{H}_2\text{O} \rightleftharpoons \text{HCO}_3^- + \text{OH}^-$
This hydrolysis produces $\text{OH}^-$ ions, leading to an increase in $[\text{OH}^-]$ concentration and making the solution basic.
Answer: an increase in $[\text{OH}^-]$
Hence, the correct answer is option: 'A'.