Question

What will you observe when red litmus paper is introduced into a solution of sodium carbonate?

Answer 1

Effect of sodium carbonate on red litmus paper

• Sodium carbonate $\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$ dissolves in water to produce sodium hydroxide $\left(\mathrm{NaOH}\right)$ and carbonic acid $\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$.
• Carbonic acid is made up of carbon dioxide $\left({\mathrm{CO}}_2\right)$ and water $\left({\mathrm{H}}_2\mathrm{O}\right)$.
• Sodium hydroxide is a strong base and carbon dioxide is a weak acid, so overall the solution is basic.

${\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{CO}\left(\mathrm{aq}\right)$

• So, sodium carbonate being basic turns red litmus blue.
• Therefore, sodium carbonate turns red litmus paper blue.