Buffer solutionsAQA A-Level Chemistry: Flashcards

What these 13 flashcards ask

Define a buffer solution.
What does an acidic buffer contain?
What does a basic buffer contain?
Give an example of an acidic buffer.
Give an example of a basic buffer.
In CH₃COOH/CH₃COONa, which species removes added H⁺?
In CH₃COOH/CH₃COONa, which species removes added OH⁻?
In NH₃/NH₄Cl, which species removes added OH⁻?
Write the expression for [H⁺] in an acidic buffer.
Why can [A⁻] be taken as the salt concentration?
Which buffer keeps blood at about pH 7.4?
Why is a buffer 'approximately' constant in pH?
Why is HCl with NaCl not a buffer?

Exam questions on Buffer solutions

A technician prepares a buffer solution by dissolving solid sodium ethanoate in a solution of ethanoic acid.
Explain how this buffer solution resists a change in pH when a small amount of sodium hydroxide solution is added.2 marks
A laboratory needs a buffer to hold a solution at an alkaline pH. The technician mixes aqueous ammonia with a solution of ammonium chloride.
Explain how this buffer resists a change in pH when a small amount of sodium hydroxide solution is added.2 marks
A student prepares a buffer by mixing 50.0 cm³ of 0.200 mol dm⁻³ methanoic acid, HCOOH, with 25.0 cm³ of 0.100 mol dm⁻³ sodium methanoate, HCOONa. For methanoic acid, $K_a = 1.78 \times 10^{-4}$ mol dm⁻³ at 298 K.
Calculate the pH of the buffer solution. Give your answer to 3 significant figures.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).