Assuming equal concentrations, arrange these solutions by pH. (From Highest to lowest)

Question

Assuming equal concentrations, arrange these solutions by pH. (From Highest to lowest)

NaOH (aq)

NH3 (aq)

Ca(OH)2 (aq)

HClO4 (aq)

HF (aq)

Answer 1

Ca(OH)₂ (aq) .. highest pH

NaOH (aq)

NH₃ (aq)

HF (aq)

HClO₄ (aq) ... lowest pH

Explanation:

Ca(OH)² and NaOH are both strong bases, but Ca(OH)2 has twice the number of OH^- ions for a given concentration, so it will have a higher pH than NaOH.

Next comes NH₃ which is a weak base, and has higher pH than the remaining two options which are both acids.

Finally, HF is a weak acid and so has a higher pH than the strong acid HClO₄, which has the lowest pH.