Intro to Buffers Practice Problems

Determine the solution with the greatest buffer capacity among the representations of solutions shown below containing one or more of the following components: H₂A, KHA, and K₂A, where H₂A is a weak diprotic acid. Note that K⁺ ions and water were omitted from the representation for clarity.

Determine what happens to the pH (increases, decreases, or remains the same) of a buffer solution containing equal concentrations of C₆H₇O₇⁻ and C₆H₆O₇²⁻on the addition of each of the following: 

(a) K₃C₆H₅O₇

(b) NaBr

(c) C₆H₈O₇

(d) HCl 

(e) K₂C₆H₆O₇ 

(f) NaOH

Identify a mixture from the following solution pairs where equal volumes of the two solutions, when mixed together, will lead to the formation of a buffer.

a) 0.13 M HCl with 0.15 M NaOH

b) 0.13 M H₂SO₄ with 0.13 M Na₂CO₃

c) 0.26 M HCN with 0.13 M KOH

d) 0.10 M NH₄Cl with 0.20 M HCl

The following diagram represents four different solutions that may contain any of these four species in varying concentrations: H₂A, KHA, and K₂A.

K⁺ ions are not shown for clarity. Identify which of these solutions is a buffer.

Identify which of the following two solutions has a higher buffer capacity:

a) 150.0 mL of 0.15 M KCN-0.15 M HCN

b) 150.0 mL of 0.15 M C₂H₃O₂-0.10 M C₂H₄O₂

Explain your choice.

Identify the buffer from the given mixtures 

Consider two buffers that are prepared by using an equal number of moles of hypochlorous acid (HClO) and sodium hypochlorite (NaClO), adding it to water to make a 2.00 L of buffer solution. In Buffer X, 1.50 mol each of hypochlorous acid and sodium hypochlorite was used. In Buffer Y, 0.150 mol of each was used. Identify the buffer that would have a higher buffering capacity.

The image below shows a buffer with equal amounts of weak acid, HA, and its conjugate base, A^–. If the column heights pertain to the amount of component present, select the image showing a scenario that does not occur because of the addition of a base or an acid

The image below shows a buffer with equal amounts of weak acid, HA, and its conjugate base, A^–. If the column heights pertain to the amount of component present, select the image that shows the buffer after a strong acid is added.

The flask on the left has a mixture of 0.2 M hypochlorous acid and 0.2 M potassium hypochlorite with bromthymol blue. The flask on the right has a solution of 0.2 M hypochlorous acid with bromthymol blue. Choose the solution that is able to resist drastic changes in pH even if small amounts of KOH are added. Explain. (K_a hypochlorous acid = 2.9×10^–8) 

A particular system uses a buffer consisting of HSO₄^- and SO₄^2-. Can this be replaced with a buffer consisting of H₂SO₄ and HSO₄^-? Briefly explain.

Identify whether the solution of the following compounds results in a buffer: 

250.0 mL 0.25 M CHCOOH and 105.0 mL of 0.050 M HCl

Write equations showing how a buffer containing CH₃NH₂ and CH₃NH₃Br neutralizes acid and base. 

Does the addition of 2.56 g HCl exceed the capacity of the 250.0 mL buffer solution that is 0.125 M of HF and 0.175 M of NaF.  

Does the addition of 1.5 g of KOH exceed the capacity of the 250.0 mL buffer solution that is 0.125 M of HF and 0.175 M of NaF.

Select the statements that correctly describe buffers.

a) The pH of a buffer solution does not change significantly when any amount of a strong acid is added.

b) An acid added to the buffer solution reacts with the weak base of the buffer.

c) The pH of a buffer solution is determined by the ratio of the concentration of conjugate base to the concentration of strong acid.

d) A buffer is generally made up of a weak acid and its conjugate base.

e) The Ka of a buffer does not change when any amount of an acid is added to the buffer solution.

Identify which of the following solutions can act as a buffer:

A buffer contains significant amounts of acetic acid and sodium acetate.

a. Write a molecular equation showing how this buffer neutralizes added acid HNO₃.

b. Write a molecular equation showing how this buffer neutralizes added base KOH.

For a buffer of pH 9.5, which of the following weak acid-conjugate base mixtures would you choose? Explain your choice.

a) CH₃COOH and NaCH₃COO

b) NH₄Cl and NH₃

c) HCOOH and NaHCOO

A buffer solution with a pH of 7.20 needs to be prepared. If the following 0.20 M solutions are available in the laboratory: HF, NaF, HClO, CH₃COOH, NaClO, CH₃COONa. Choose a combination that would be best to use to prepare the buffer.

K_a HF = 6.8×10^–4       

K_a HClO = 3.0×10^–8          

K_a CH₃COOH = 1.8×10^–5         

Identify the buffer from the given mixtures 

Identify whether the solution of the following compounds results in a buffer: 

250.0 mL 0.25 M CHCOOH and 105.0 mL of 0.050 M HCl

Which of the following is a buffer?