Quick questions on Acid-Base Equilibria (Topic 17) - Edexcel A-Level Chemistry

3short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What are buffer solutions?

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To calculate a buffer pH, rearrange the

K_a

expression to

[\text{H}^+] = K_a \times \dfrac{[\text{HA}]}{[\text{A}^-]}

. At the half-equivalence point of a weak-acid titration,

[\text{HA}] = [\text{A}^-]

, so

[\text{H}^+] = K_a

and

\text{pH} = \text{p}K_a

, a useful way to find

K_a

from a curve.

What is q1?

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Calculate the pH of

0.010\ \text{mol dm}^{-3}

hydrochloric acid. [1 mark]

What is q2?

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Explain how an acidic buffer resists a rise in pH when a small amount of alkali is added. [2 marks]

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