Question

Which one of the following has highest pH?

• A. Distilled water
• B. 1 M ${NH}_3$
• C. 1 M $NaOH$
• D. Water saturated with chlorine

Answer 1

The correct option is C

1 M $\mathrm{NaOH}$

The explanation for the correct option (C):

• pH refers to the potential of Hydrogen ($\mathrm{H}$).
• pH is a scale that is used to determine the acidic and basic strength of the solution.
• When the pH of the solution is less than 7, then the solution is said to be acidic in nature. A pH value greater than 7 indicates that the solution is basic in nature while the pH value equal to 7 indicates that the solution is neutral in nature.
• Sodium hydroxide ($\mathrm{NaOH}$) is a strong base. 1 M $\mathrm{NaOH}$ solution is strongly basic in nature and therefore, it has the highest pH (around 13) among the given options.
• $\mathrm{NaOH}\left(\mathrm{aq}\right)\to {\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)$

The explanation for the incorrect options:

(A)

• Distilled water is a form of water that is completely free of ions.
• The pH of distilled water is neutral, meaning it is neither acidic nor basic. Hence, the pH of distilled water is approximately 7.

(B)

• Ammonia (${\mathrm{NH}}_3$) is a comparatively weaker base (due to the absence of Hydroxide ions (${\mathrm{OH}}^{-}$)) than $\mathrm{NaOH}$. Hence, the pH of 1 M ${\mathrm{NH}}_3$ (around 11) is less than $\mathrm{NaOH}$.

(D)

• Water (${\mathrm{H}}_2\mathrm{O}$) saturated with Chlorine (${\mathrm{Cl}}_2$) is acidic in nature and therefore, its pH is less than 7 and it is the lowest among the given options.

Final Answer: Hence, option (C) is correct. 1 M $\mathrm{NaOH}$ has the highest pH.