which of the following solutions containing one mole per dm³ of the compound would have the lowest PH?

Correct Answer is : hydrochloric acid

Correct Answer is : hydrochloric acid

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WAEC Chemistry 2019 Paper

Question : 19

Total: 50

^3

of the compound would have the lowest PH?

Solution:

Concept:

Lower pH indicates a more acidic solution. The compound that releases the most hydrogen ions will give the lowest pH.

Explanation:

Hydrochloric acid is a strong acid. It fully dissociates in water as

\mathrm{HCl \rightarrow H^+ + Cl^-}

At a concentration of one mole per dm

^3

, it produces a high concentration of

\mathrm{H^+}

ions, giving a very low pH.

Ethanoic acid is a weak acid, so it only partially ionises and gives a higher pH.

Sodium chloride is a neutral salt, giving pH around 7.

Sodium hydrogentrioxocarbonate(iv) forms a slightly alkaline solution, so its pH is above 7.

Therefore, hydrochloric acid has the lowest pH.

Answer:

Option B. Hydrochloric acid.

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