Edexcel IAL Chemistry 14.7 pH of a strong acid

Treat a strong monoprotic acid as fully dissociated, then use moles and total volume where mixing or dilution changes the hydrogen ion concentration before finding pH.

Exam points

Calculate pH directly as -log10[H+] for fully dissociated strong monoprotic acids.
Use acid-base moles and total volume before finding pH for a mixture with excess acid.
Predict the pH decrease when strong-acid concentration is increased or diluted.

[Maximum number: 1]

Propanoic acid is a weak acid.

Calculate the pH of $0.500 \mathrm{~mol} \mathrm{dm}^{-3}$ hydrochloric acid at $25^{\circ} \mathrm{C}$ .

calculation of pH

$\begin{aligned} \mathrm{pH}=-\log _{10}(0.500)=0.30103 / 0.301 / 0.30 / 0.3 \text { Ignore SF } \end{aligned}$

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14.7—The pH of a strong acid question 1