Question

Which one of the following will turn red litmus blue?

• A. Vinegar
• B. Baking soda solution
• C. Lemon juice
• D. Soft drinks

Answer 1

The correct option is B

Baking soda solution

The explanation for the correct option (B):

• Bases are the chemical substances that dissociate to produce Hydroxide ions (${\mathrm{OH}}^{-}$) ions when dissolved in Water (${\mathrm{H}}_2\mathrm{O}$).
• Bases have a bitter taste.
• Bases turn red litmus blue.
• Baking soda (${\mathrm{NaHCO}}_3$) is a base and its aqueous solution is basic in nature. Hence, it will turn red litmus blue.
• ${\mathrm{NaHCO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{HCO}}_3^{-}\left(\mathrm{aq}\right)$

${\mathrm{HCO}}_3^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

The explanation for the incorrect options:

• (A) The dilute solution of Acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$) is Vinegar (${\mathrm{CH}}_3\mathrm{COOH}$). Vinegar is acidic in nature. Hence, it turns blue litmus red.
• (C) Lemons contain Citric acid (${\mathrm{C}}_6{\mathrm{H}}_8{\mathrm{O}}_7$). Hence, lemon juice is acidic in nature and it turns blue litmus red.
• (D) Soft drinks generally contain Phosphoric acid (${\mathrm{H}}_3{\mathrm{PO}}_4$). Hence, soft drinks are acidic in nature and it turns blue litmus red.

Final Answer: Hence, option (B) is correct. Baking soda solution will turn red litmus blue.