Question 1

Of the following solutions, which has the greatest buffering capacity? A)0.543 M NH₃ and 0.555 M NH₄Cl B)0.087 M NH₃ and 0.088 M NH₄Cl C)0.234 M NH₃ and 0.100 M NH₄Cl D)0.100 M NH₃ and 0.455 M NH₄Cl E)They are all buffer solutions and would all have the same capacity.

Accepted Answer

A

Question 2

Which of the following could be added to a solution of potassium fluoride to prepare a buffer?
A)sodium hydroxide
B)potassium acetate
C)hydrochloric acid
D)sodium fluoride
E)ammonia

Accepted Answer

C

Question 3

Which one of the following pairs cannot be mixed together to form a buffer solution? A)HONH₂, HONH₃Cl B)NaCl, HCl C)RbOH, HF D)KOH, HNO₂ E)H₂SO₃, KHSO₃

Accepted Answer

In order to form a buffer solution, we need a weak acid and its conjugate base or a weak base and its conjugate acid. However, in option B, NaCl and HCl are both strong electrolytes and cannot act as a weak acid and its conjugate base.

Question 4

What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride?
A)The concentration of hydronium ions will increase significantly.
B)The concentration of fluoride ions will increase as will the concentration of hydronium ions.
C)The concentration of hydrogen fluoride will decrease and the concentration of fluoride ions will increase.
D)The concentration of fluoride ion will decrease and the concentration of hydrogen fluoride will increase.
E)The fluoride ions will precipitate out of solution as its acid salt.

Accepted Answer

Adding a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride will increase the concentration of hydronium ions (H3O+), which shifts the equilibrium of the reaction HF ⇌ H+ + F- to the left, according to Le Chatelier's principle. This results in an increase in the concentration of hydrogen fluoride (HF) and a decrease in the concentration of fluoride ions (F-).

Question 5

A solution containing which one of the following pairs of substances will be a buffer solution?
A)NaI, HI
B)KBr, HBr
C)RbCl, HCl
D)CsF, HF
E)none of the above

Accepted Answer

A buffer solution is a solution that can resist changes in pH upon the addition of small amounts of acid or base. To be a buffer solution, it must contain a weak acid and its corresponding conjugate base or a weak base and its corresponding conjugate acid. In option D, CsF is a weak base and HF is a weak acid, thus forming a buffer solution. The other options do not contain a weak acid and its corresponding conjugate base or a weak base and its corresponding conjugate acid, so they are not buffer solutions.

Question 6

The addition of hydrochloric acid and ________ to water produces a buffer solution. A)HC₆H₅O B)NaOH C)NH₃ D)HNO₃ E)NaNO₃

Accepted Answer

A buffer solution is formed when a weak base and its conjugate acid are present. NH₃ (ammonia) is a weak base, and when combined with HCl, it forms NH₄Cl, which acts as a buffer in solution.

Question 7

Which of the following could be added to a solution of acetic acid to prepare a buffer?
A)sodium acetate only
B)sodium acetate or sodium hydroxide
C)nitric acid only
D)hydrofluoric acid or nitric acid
E)sodium hydroxide only

Accepted Answer

To prepare a buffer, we need a weak acid and its conjugate base. Acetic acid is a weak acid and its conjugate base is sodium acetate. Therefore, adding sodium acetate to a solution of acetic acid will prepare a buffer. Addition of sodium hydroxide would react with acetic acid to make sodium acetate, which will further react with the remaining acetic acid to maintain the buffer. Nitric acid and hydrofluoric acid are strong acids and cannot be used to prepare a buffer.

Question 8

The primary buffer system that controls the pH of the blood is the ________ buffer system.
A)carbon dioxide, carbonate
B)carbonate, bicarbonate
C)carbonic acid, carbon dioxide
D)carbonate, carbonic acid
E)carbonic acid, bicarbonate

Accepted Answer

The primary buffer system that controls the pH of the blood is the carbonic acid, bicarbonate buffer system. Carbonic acid (H2CO3) can dissociate to form hydrogen ions (H+) and bicarbonate ions (HCO3-). If there is an excess of hydrogen ions (resulting in lower pH), they can combine with the bicarbonate ions to form carbonic acid, thus removing excess hydrogen ions and bringing the pH back to its normal range. Similarly, if there is a deficit of hydrogen ions (resulting in higher pH), carbonic acid can dissociate to form more hydrogen ions and bicarbonate ions, thus bringing the pH back to its normal range.

Question 9

A solution containing which one of the following pairs of substances will be a buffer solution?
A)KI, HI
B)AgBr, HBr
C)CuCl, HCl
D)CsI, HI
E)none of the above

Accepted Answer

A buffer solution requires a weak acid or base and its conjugate salt. All the pairs listed involve strong acids (HI, HBr, HCl) and their salts, which do not form buffer solutions.

Question 10

The addition of sodium hydroxide and ________ to water produces a buffer solution. A)HCl B)NaC₂H₃O₂ C)NaF D)NH₃ E)none of the above

Accepted Answer

The answer of The addition of sodium hydroxide and ________...

Question 11

The Henderson-Hasselbalch equation is ________. A)[H⁺] = K_a + B)pH = pK_a - log C)pH = pK_a + log D)pH = pK_a + log E)pH = log

Accepted Answer

The answer of The Henderson-Hasselbalch equation is ________. A)[H⁺] = K_a...

Question 12

Which one of the following pairs cannot be mixed together to form a buffer solution? A)NH₃, NH₄Cl B)NaC₂H₃O₂, HCl (C₂H₃O₂^- = acetate) C)RbOH, HBr D)KOH, HF E)H₃PO₄, KH₂PO₄

Accepted Answer

RbOH and HBr cannot be mixed together to form a buffer solution because a buffer solution requires a weak acid and its conjugate base, or a weak base and its conjugate acid. RbOH is a strong base, and HBr is a strong acid, so they cannot form a buffer system.

Question 13

The addition of hydrofluoric acid and ________ to water produces a buffer solution. A)HCl B)NaNO₃ C)NaCl D)NaOH E)NaBr

Accepted Answer

Hydrofluoric acid (HF) is a weak acid, and when it is added to water, it undergoes partial ionization to form H+ ions and F- ions. This can be represented as: 
HF + H2O ⇌ H3O+ + F- 
The addition of a strong base such as NaOH to this solution will react with the H+ ions to form water and the F- ions will react with the Na+ ions to form NaF. This reaction will help to maintain the pH of the solution at a relatively constant level, creating a buffer solution. Therefore, the correct choice is D) NaOH.

Question 14

The addition of hydrochloric acid and ________ to water produces a buffer solution. A)HC₆H₅O B)NaOH C)NaCl D)C₂H₅NH₂ E)none of the above

Accepted Answer

A buffer solution is typically made from a weak acid and its conjugate base or a weak base and its conjugate acid. Hydrochloric acid (a strong acid) and C₂H₅NH₂ (a weak base) can form a buffer solution when mixed in appropriate amounts.

Question 15

In a solution, when the concentrations of a weak acid and its conjugate base are equal, ________. A)the system is not at equilibrium B)the buffering capacity is significantly decreased C)the -log of the [H⁺] and the -log of the K_a are equal D)All of the above are true.

Accepted Answer

When the concentrations of a weak acid and its conjugate base are equal, the system is at half-equivalence point and the -log of the [H⁺] and the -log of the K_a are equal. This is because at half-equivalence, the concentrations of the acid and its conjugate base are equal, which means that the equilibrium constant, Ka, is equal to the dissociation constant of the conjugate base, Kb. As a result, the pH of the solution is equal to the pKa of the weak acid. The buffering capacity is not significantly decreased at half-equivalence point.

Question 16

Which one of the following pairs cannot be mixed together to form a buffer solution? A)C₅H₅N, C₅H₅NHCl B)HC₂H₃O₂, NaOH (C₂H₃O₂^- = acetate) C)KOH, HI D)NH₂CH₃, HCl E)NaClO, HNO₃

Accepted Answer

A buffer solution requires a weak acid and its conjugate base or a weak base and its conjugate acid. Choice C contains a strong base (KOH) and a strong acid (HI), which cannot form a buffer solution.

Question 17

Which of the following could be added to a solution of acetic acid to prepare a buffer?
A)sodium hydroxide
B)hydrochloric acid
C)nitric acid
D)more acetic acid
E)None of the above can be added to an acetic acid solution to prepare a buffer.

Accepted Answer

A buffer solution can be prepared by adding a strong base like sodium hydroxide to acetic acid, which will partially neutralize the acetic acid and form its conjugate base, acetate, creating a buffer system.

Question 18

Of the following solutions, which has the greatest buffering capacity? A)0.521 M HC₂H₃O₂ and 0.217 M NaC₂H₃O₂ B)0.821 M HC₂H₃O₂ and 0.713 M NaC₂H₃O₂ C)0.365M HC₂H₃O₂ and 0.497 M NaC₂H₃O₂ D)0.121 M HC₂H₃O₂ and 0.116 M NaC₂H₃O₂

Accepted Answer

The buffering capacity of a solution is directly proportional to the concentrations of both the weak acid and its conjugate base. Therefore, the solution with the greatest buffering capacity is the one with the highest concentrations of both the weak acid and its conjugate base. In this case, that is solution B.

Question 19

What are the principal organs that regulate the pH of the carbonic acid-bicarbonate buffer system in the blood?
A)kidneys, liver
B)lungs, kidneys
C)spleen, liver
D)lungs, skin
E)brain stem, heart

Accepted Answer

The lungs and kidneys are the principal organs that regulate the pH of the carbonic acid-bicarbonate buffer system in the blood. The lungs regulate the partial pressure of carbon dioxide (CO2), which determines the amount of carbonic acid (H2CO3) in the blood. The kidneys regulate the amount of bicarbonate (HCO3-) ions in the blood. Together, the lungs and kidneys maintain a balance between the production and elimination of carbonic acid and bicarbonate ions to keep the blood pH within a normal range.

Question 20

Which of the following could be added to a solution of sodium acetate to produce a buffer?
A)acetic acid only
B)acetic acid or hydrochloric acid
C)hydrochloric acid only
D)potassium acetate only
E)sodium chloride or potassium acetate

Accepted Answer

A buffer contains a weak acid and its corresponding conjugate base. Sodium acetate is the salt of a weak acid (acetic acid) and a strong base (sodium hydroxide), so we need to add acetic acid to provide the weak acid component. Hydrochloric acid cannot be used as it is a strong acid and would not form a buffer. Potassium acetate is a salt of a weak acid (acetic acid) and a strong base (potassium hydroxide), but we already have the salt component in our solution, so adding more of it would not create a buffer. Sodium chloride is a salt of a strong acid and a strong base, so it would not be appropriate for making a buffer.

Quiz 17: Additional Aspects of Aqueous Equilibria

Of the following solutions, which has the greatest buffering capacity?

Which of the following could be added to a solution of potassium fluoride to prepare a buffer?

Which one of the following pairs cannot be mixed together to form a buffer solution?

What change will be caused by addition of a small amount of HCl to a solution containing fluoride ions and hydrogen fluoride?

A solution containing which one of the following pairs of substances will be a buffer solution?

The addition of hydrochloric acid and ________ to water produces a buffer solution.

Which of the following could be added to a solution of acetic acid to prepare a buffer?

The primary buffer system that controls the pH of the blood is the ________ buffer system.

A solution containing which one of the following pairs of substances will be a buffer solution?

The addition of sodium hydroxide and ________ to water produces a buffer solution.

The Henderson-Hasselbalch equation is ________.

Which one of the following pairs cannot be mixed together to form a buffer solution?

The addition of hydrofluoric acid and ________ to water produces a buffer solution.

The addition of hydrochloric acid and ________ to water produces a buffer solution.

In a solution, when the concentrations of a weak acid and its conjugate base are equal, ________.

Which one of the following pairs cannot be mixed together to form a buffer solution?

Which of the following could be added to a solution of acetic acid to prepare a buffer?

Of the following solutions, which has the greatest buffering capacity?

What are the principal organs that regulate the pH of the carbonic acid-bicarbonate buffer system in the blood?

Which of the following could be added to a solution of sodium acetate to produce a buffer?