WorksheetsBuffers
Total questions: 61
Worksheet time: 31mins
What is the function of buffer systems in a solution?
They increase the pH
They decrease the pH
They resist changes in pH after the addition of small amounts of acids and bases
They neutralize all acids and bases
Acid buffers are composed of ______ and its conjugate base (salt).
weak acid
strong acid
weak base
strong base
Basic buffers are composed of weak base and its ______ (salt).
conjugate acid
conjugate base
neutral compound
strong acid
Fill in the blank for the Henderson Hasselbach equation for an acid buffer: pH = pKₐ + log ([____]/[acid]); salt is ionized; acid is unionized.
salt
base
water
buffer
Fill in the blank for the Henderson Hasselbach equation for a basic buffer: pH = pKₐ + log ([base]/[____]); salt is ionized; base is unionized.
salt
acid
water
buffer
Which of the following statements is true about the pH of a buffer?
The pH of a buffer is affected by the absolute concentration of salt and acid/base.
The pH of a buffer is affected only by the ratio of concentration of salt over acid or base over salt since the dissociation constant is a constant.
The pH of a buffer is not affected by salt or acid/base concentration at all.
The pH of a buffer changes randomly.
If the ratio of salt over acid or base over salt is identical, regardless of the molar concentrations of the salt and acid, what happens to the pH?
The pH will increase.
The pH will decrease.
The pH will remain unaffected.
The pH will fluctuate.
What role can a conjugate acid-base pair play in a buffer system?
Only as a proton donor
Only as a proton acceptor
As both a proton donor and acceptor
Neither
Fill in the blank: The ionization reaction for an acid buffer is ________. (Provide the full chemical equation as shown in the notes.)
HA₁ + H₂O ⇌ A₁⁻ + H₃O⁺
HA₁ + H₂O ⇌ HA₁⁻ + H₃O⁺
HA₁ + H₂O ⇌ A₁ + H₃O⁺
HA₁ + H₂O ⇌ A₁⁻ + H₂O
Fill in the blank: The hydrolysis reaction for an acid buffer is ________. (Provide the full chemical equation as shown in the notes.)
A₁⁻ + H₂O ⇌ OH⁻ + HA₁
HA₁ + OH⁻ ⇌ A₁⁻ + H₂O
A₁⁻ + H₂O ⇌ H₃O⁺ + HA₁
HA₁ + H₂O ⇌ A₁⁻ + H₃O⁺
What happens when an acid HA₂ is added to the buffer system?
HA₂ + A₁⁻ ⇌ A₂⁻ + HA₁
HA₂ + HA₁ ⇌ A₂⁻ + A₁⁻
HA₂ + A₂⁻ ⇌ HA₁ + A₁⁻
HA₂ + A₁⁻ ⇌ HA₁ + A₂⁻
What happens to the ratio of [S]:[A] when an acid or base is added to the buffer system?
The ratio of [S]:[A] remains constant.
The ratio of [S]:[A] increases significantly.
The ratio of [S]:[A] decreases to zero.
The ratio of [S]:[A] fluctuates randomly.
Fill in the blank: When a base B₂⁻ is added to the buffer, the reaction is ________.
B₂⁻ + HA₁ ⇌ A₁⁻ + HB₂
B₂⁻ + A₁⁻ ⇌ HA₁ + HB₂
B₂⁻ + HB₂ ⇌ A₁⁻ + HA₁
B₂⁻ + HA₁ ⇌ HB₂ + A₁⁻
Fill in the blank: The ionization reaction for a basic buffer is _________.
B₁ + H₂O ⇌ B₁H⁺ + OH⁻
B₁H⁺ + OH⁻ ⇌ B₁ + H₂O
HA + H₂O ⇌ H₃O⁺ + A⁻
HA ⇌ H⁺ + A⁻
Fill in the blank: The hydrolysis reaction for a basic buffer is _________.
B₁H⁺ + H₂O ⇌ B₁ + H₃O⁺
B₁ + H₂O ⇌ B₁H⁺ + OH⁻
B₁H⁺ + OH⁻ ⇌ B₁ + H₂O
B₁ + H₃O⁺ ⇌ B₁H⁺ + H₂O
When an acid HA₂ is added to a basic buffer, which reaction occurs?
A) B₁ + HA₂ ⇌ HB₁⁺ + A₂⁻
B) B₁H⁺ + B₂ ⇌ B₂H⁺ + B₁
C) B₁ + H₂O ⇌ B₁H⁺ + OH⁻
D) HB₁⁺ + H₂O ⇌ B₁ + H₃O⁺
When a base B₂ is added to a basic buffer, the ratio of [B]:[S] remains constant.
True
False
Fill in the blank: When an acid HA₂ is added, the ratio of [S]:[A] remains _________
constant
variable
zero
increasing
Which of the following is NOT a factor affecting buffering action by a given acid-base pair?
pH desired
pKa or pKb
Concentrations of buffering agents
Temperature of the solution
Chemical stability of buffering agents
Buffering action by a given acid-base pair is possible over a limited range. Which parameter should be considered when selecting a buffer?
pH desired
pKa or pKb
Concentrations of buffering agents
Chemical stability of buffering agents
All of the above
Fill in the blank: Always choose buffers within range where pH = pKa ____ 2.
±
×
÷
∓
Chemical stability of buffering agents is a factor to consider when choosing a buffer.
True
False
The concentration of buffering agents does not affect buffering action.
True
False
Buffers protect preparations from large swings in _____.
pH
temperature
volume
pressure
What is the term used to describe the strength of a buffer?
Buffer value
Buffer effect
Buffer capacity
All of the above
Fill in the blank: There is a _____ through which the buffers are effective.
limit
door
window
channel
Buffer capacity is a function of which of the following?
Kₐ
[H⁺]
Molar components of the buffer
All of the above
Fill in the blank: C is the _____ concentration of the buffer.
molar
ionic
acidic
basic
What is buffer capacity defined as?
The ratio of change in gram equivalent weight of an acid or base needed to produce a particular change in pH in 1L of the buffer solution
The amount of acid required to neutralize a base
The pH at which a buffer is most effective
The concentration of acid in a solution
Fill in the blank: The formula for buffer capacity (β) is β = ____ / ΔpH.
B
A
C
D
Maximum buffer capacity is reached when Kₐ = [H⁺].
True
False
The capacity of a buffer depends on the ionic dissociation constant, _______ ion concentration, and the molar concentration of the buffer. (Fill in the blank)
hydrogen
sodium
chloride
potassium
What is the unit of buffer capacity?
mole.liter⁻¹.pH⁻¹
gram equivalent.liter⁻¹.pH⁻¹
gram.liter⁻¹.pH⁻¹
mole equivalent.liter⁻¹.pH⁻¹
No units are usually stated for buffer capacity.
True
False
Fill in the blank: The first step in buffer preparation is to decide on what ____ is needed.
pH
volume
temperature
concentration
Fill in the blank: For maximum buffer capacity, choose the acid-base pair so that ____ is close to [H+].
Kₐ
pH
K_b
pK_a
Fill in the blank: Use ____ equation to determine the ratio of proton acceptor to donor in buffer preparation.
Henderson Hasselbach
Arrhenius
Boyle's
Van't Hoff
Fill in the blank: Choose total concentration of acid-base pair so that β falls in the range of ____ to ____.
0.01 to 0.1
0.1 to 1.0
1.0 to 10.0
0.001 to 0.01
Fill in the blank: The final step in buffer preparation is to verify the ____ of the prepared buffer.
pH
temperature
volume
color
Calculate the pH of the buffer solution prepared from 0.03M phenobarbital and 0.02M sodium phenobarbital. pKa of phenobarbital is 7.4. Fill in the blank: The pH of the buffer solution is _____
7.22
7.40
6.80
7.00
If the addition of 0.1 mole of HCl (Mol. Wt. 36.5) to one liter of a buffer solution caused a drop in the pH by 0.4 units, calculate the capacity of the buffer.
0.25 mol/L/pH unit
0.40 mol/L/pH unit
0.10 mol/L/pH unit
0.50 mol/L/pH unit
The buffer capacity of a solution is 0.02. Calculate the volume of 1N NaOH (Mol. Wt. 40) to be added to one liter of the buffer to change the pH by 1 unit.
50 mL
10 mL
100 mL
5 mL
What concentrations of sodium acetate and acetic acid are needed to prepare a buffer with pH of 4.76? pKₐ of acetic acid is 4.76.
Equal concentrations of sodium acetate and acetic acid
Twice the concentration of sodium acetate compared to acetic acid
Half the concentration of sodium acetate compared to acetic acid
Ten times the concentration of sodium acetate compared to acetic acid
If you were to add 0.8 M acetic acid solution to 0.2 M sodium acetate solution, what would be the buffer capacity of the resulting solution? (pKa=4.76)
0.368
0.294
4.16
0.0736
Fill in the blank: Most drugs are ________ weak electrolytes.
organic
inorganic
metallic
synthetic
Which property of drugs has extensive physiologic implications?
Solubility
Ionization
Color
Taste
Fill in the blank: Ionization of weak electrolytes is ______ dependent.
pH
temperature
pressure
volume
A drug exists in ________ or ________ form depending on the pH.
unionized, ionized
solid, liquid
acidic, basic
dilute, concentrated
Ionized form is relatively more soluble in aqueous solutions than unionized.
True
False
Unionized form is relatively more lipid soluble and hence more permeable through lipid membranes.
True
False
Change in pH can cause a big change in the degree of ionization and hence corresponds to a change in which of the following?
Solubility
Dissolution rate
Partition coefficient
All of the above
The pH of body fluids ranges from _____
1-8
6-9
2-7
4-10
Degree of ionization can have a profound effect on which of the following aspects of drugs?
Absorption
Distribution
Elimination
All of the above
What is the main function of buffers?
Increase pH
Protect or shield against change in pH
Decrease pH
Cause chemical reactions
Buffers are used in ________ studies to ensure stability of drugs.
Drug stability studies
Pharmacokinetic studies
Toxicology studies
Bioavailability studies
Name one type of physiologic buffer in the blood that helps maintain pH at 7.35-7.45.
Hemoglobin
Glucose
Cholesterol
Insulin
Eye fluids are maintained at pH _______.
7.4
6.8
8.0
5.5
Which of the following is NOT a physiologic buffer in the blood?
A) Hemoglobin
B) Bicarbonates
C) Phosphates
D) Glucose
Proteins, carbonic acids, and other organic acids in tears help maintain the pH of which body fluid?
Blood
Eye fluids
Saliva
Urine
The capacity of the buffer system is lowest when the pH is equal to its pKa
True
False
Which of the following solutions act as a buffer system?
A. A solution of 0.1 M Benzoic acid (weak acid)
B. A solution of 0.1 M Sodium benzoate
C. A solution of 0.1 M benzoic acid and 0.1 M Sodium benzoate
D. A solution of 0.1 M sodium benzoate and 0.1 M potassium benzoate
