16 past paper MCQs on Buffer Solutions, from the Chemical Equilibrium unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.A buffer solution is not formed by: (MDCAT 2020)
Correct answer: (d) $\mathrm{HCl+NaCl}$
A buffer needs a weak acid or base with its own salt; HCl is a strong acid, so this mixture has no reserve to soak up added acid or alkali.
2.Which of the following is basic buffer? (UHS MDCAT 2025)
Correct answer: (a) NH4OH/NH4Cl
A basic buffer is a weak base with the salt of that base, here ammonium hydroxide with ammonium chloride.
3.What happens when H+ is added to ammonium hydroxide and ammonium chloride buffer? (UHS MDCAT 2025)
Correct answer: (b) reaction will move reverse
The added protons are taken up by the ammonium hydroxide, driving the ionization back and holding the pH.
4.Select the buffer solution having highest pH: (NUMS MDCAT 2024)
Correct answer: (d) 0.1M CH3COOH, 0.15M CH3COO-
The pH rises with the ratio of salt to acid, which is largest in the last mixture.
5.Which of the following is not the use of Buffer solution? (SZABMU MDCAT 2023)
Correct answer: (d) Predict the concentration of a substance
A buffer holds a pH steady; it measures no concentration.
6.The reaction of a weak acid and its salt with a strong base produces: (PMC MDCAT 2022)
Correct answer: (b) A buffer with pH <7
A weak acid with its salt is an acidic buffer, holding a pH below seven.
7.The pH of a solution can be kept constant by: (PMC MDCAT 2022)
Correct answer: (c) buffer solution
A buffer resists a change of pH when a little acid or alkali is added.
8.Which of the following solutions will act as a buffer? (PMC MDCAT 2022)
Correct answer: (a) HN02 and NaN02
Nitrous acid with its sodium salt is a weak acid and its conjugate base, which is a buffer.
9.The pH of an acidic buffer depends upon the concentration of acid, concentration of salt and: (PMC MDCAT 2022)
Correct answer: (a) pKa of acid used in it
The Henderson equation gives the pH as the $\mathrm{p}K_a$ plus the log of the salt to acid ratio.
10.Addition of extra CH3COONa in acetate buffer soluton wlll: (PMC MDCAT 2022)
Correct answer: (c) Increase pH
More salt raises the ratio of acetate to acid, so the pH rises.
11.The addition of an acid or H+ Ions to acetic acid buffer will: (PMC MDCAT 2022)
Correct answer: (c) Have no effect on the pH
The acetate ions take up the added protons, so the pH scarcely moves.
12.The pH of human blood is: (NUMS MDCAT 2022)
Correct answer: (a) 7.35 to 7.45
Blood is held between pH $7.35$ and $7.45$ by its buffers.
13.The pH of 10-2 M aqueous solution of sodium hydroxide is: (UHS MDCAT 2019)
Correct answer: (c) 12
$10^{-2}\,\mathrm{M}$ alkali gives pOH $2$, so the pH is $12$.
14.The Ka values of HCI, CH3COOH, HF, and H2SO4 are 107, 1.85 x 10-5, 6.7 x 10-5 and 102 respectively. The decreasing order of acidic strength is: (UHS MDCAT 2019)
Correct answer: (b) HCI > H2SO4 > HF > CH3COOH
The larger the acid dissociation constant the stronger the acid.
15.According to Lowry – Bronsted Acid & Base Concept, H2O is: (UHS MDCAT 2018)
Correct answer: (c) An amphoteric species
Water can give a proton or take one, so it is amphoteric.
16.Human blood maintains its pH between (UHS MDCAT 2016)
Correct answer: (d) 7.35 – 7.40
Blood is buffered between about pH $7.35$ and $7.45$.