Question

Two test tubes containing water are labelled A and B. Few drops of hydrochloric acid are added to test tube A and acetic acid to test tube B. Which of the following statements are true regarding the number of $H^{+}$ ions in the test tubes?

• A. Test tube B has more number of $H^{+}$ ions than test tube A
• B. It cannot be predicted
• C. Test tube A has more number of $H^{+}$ ions than test tube B
• D. Both the test tubes have equal number of $H^{+}$ ions

Answer 1

The correct option is C Test tube A has more number of $H^{+}$ ions than test tube B

Acetic acid $\left({\text{CH}}_3\text{COOH}\right)$ is a weak acid and gets partially ionised in water. This means that not all molecules of acetic acid ionise to form ${\text{CH}}_3{\text{COO}}^{-}$ and ${\text{H}}^{+}$ ions.

$C{H}_{3}COOH\left(aq\right)\leftrightharpoons H^{+}\left(aq\right)+C{H}_{3}CO{O}^{-}\left(aq\right)$

Hydrogen chloride $\left(\text{HCl}\right)$ is a strong acid. It ionises completely in water into ${\text{H}}^{+}$ and ${\text{Cl}}^{-}$ ions.

$HCl\left(aq\right)\stackrel{dissociate}{\to }{H}^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$

Therefore, hydrochloric acid will have more number of ${\text{H}}^{+}$ ions in aqueous solution than acetic acid.