Buffer Solutions

Question 1

What is a buffer solution?

Answer 1

• Resist changes in pH upon addition of small amounts of strong acid or strong base
• Resistive action is a result of the equilibrium which is set up between the weak acid and the salt

Question 2

What do buffer solutions consist of?

Answer 2

• Weak acid and it’s salt(conjugate base) or a weak base and it’s salt(conjugate acid)
• Can also be composed of mixtures of salts of polyprotic acids

Question 3

What is essential for both conjugate species in a buffer?

Answer 3

•Have to be comparable(or same) concentrations

Question 4

What is the equation for a buffer solution?

Answer 4

.

Question 5

In a buffer solution, what does HA represent?

Answer 5

•Weak acid

Question 6

In a buffer solution, what does H+ represent?

Answer 6

•Hydrogen ion component of the dissolved salt

Question 7

In a buffer solution, what does A- represent?

Answer 7

•The anion component of the salt

Question 8

Write the dissociation constant for a weak acid

Answer 8

.

Question 9

What occurs when an alkali is added to the standard acid buffer solution?

Answer 9

•The hydronium ions mop it up- the ions are regenerated as the equilibrium moves to the right and some of the acid is broken down into hydronium ions and anions

Question 10

What occurs when an acid is added to the standard acid buffer solution?

Answer 10

•The anions combine with the substance and pH is once again restored

Question 11

What are the common buffer solutions used in laboratories?

Answer 11

.

Question 12

Why are buffers important for enzymes?

Answer 12

• Keep the right pH for enzymes to function-enzymes only work under very precise conditions
• If pH strays too far from margin, enzymes slow or stop working and organism dies

Question 13

What are the applications for buffer solutions industrially?

Answer 13

• Useful In fermentation processes
• Setting the correct conditions for the dyes used in colouring fabrics

Question 14

Illustrate a buffer solution of acetic acid and sodium acetate in action

Answer 14

.

Question 15

Illustrate the Henderson hasslebach equation for an acid buffer

Answer 15

.

Question 16

Illustrate the Henderson hasslebach equation for an basic buffer

Answer 16

.

Question 17

Describe the buffer curve

Answer 17

• Vertical axis shows the pH of the buffered solution
• Horizontal axis shows the composition of the buffer(on the left hand side of the plot, most of the buffer is in the form of salt and on the right side, most of the buffer is in the form of acid-or base)
• As acid is added-pH decreases and the buffer shifts towards greater acid concentration
• As base is added, pH increases and buffer shifts toward greater salt concentration
• Slope of curve flattest where pH3 is equal to pK value for the buffer-buffering capacity greatest here because a shift in relative concentrations of acid(or base) produces only a small change in pH of the solution
• At pH values higher than pH1- slope of curve much higher and a shift in the relative concentrations of acid(base) produces a large change in pH of the solution

Question 18

Draw the buffer curve

Answer 18

.

Question 19

Describe buffer capacity?

Answer 19

• The ability of a buffer to suppress changes in pH
• The amount of an acid or base that can be added to a volume of a buffer solution before pH changes significantly
• Buffering capacity increases as the molar concentration(molarity) of the buffer salt/acid solution increases
• The closer the buffered pH is to the pKa, the greater the buffering capacity
• When buffer is diluted- it’s capacity decreases but pH does not change

Question 20

What factors determine the buffering capacity of a solution?

Answer 20

• The concentration of the buffer (the higher the concentration. The larger the buffering capacity)
• How close the pKa of the buffer is compared to the pH of the solution(the closer it is, the greater the buffer capacity

Question 21

Illustrate the buffer capacity

Answer 21

.

Question 22

What are the most important buffer systems within an organism?

Answer 22

• Hydrogen carbonate
• Proteins
• Hydrogen phosphate

Question 23

Describe hydrogen carbonate as a buffer

Answer 23

• Main buffer of extracellular fluids- makes more than half the buffer capacity of blood
• Consists of HCO3- and H2CO3

Question 24

What causes the buffer effect of proteins?

Answer 24

•Caused by their amphoteric character

Question 25

What is the most important buffer system in the blood?

Answer 25

•Oxyhemoglobin

Question 26

Which other substances do proteins buffer besides blood?

Answer 26

* Plasma pH(mainly albumin) * Intracellular fluids

Question 27

Describe hydrogen phosphate as a buffer

Answer 27

* Composed of HPO4(2-) and H2PO4- * Main buffer system of urines and Intracellular fluids

Question 28

Outline the three main buffers in the human body and their components

Answer 28

.

Question 29

At what pH do most biological processes proceed?

Answer 29

•7 (range from 6-9)

Question 30

Why is the evaluation of acid-base equilibrium an important factor for the examination of body condition?

Answer 30

•Biochemical processes rely heavily on pH of the environment and even a small change from the stable values can result in their slowing down or stopping

Question 31

What might cause disorders of acid-base balance?

Answer 31

* Formation of ketone bodies in diabetes * Formation of lactate during hypoxia * Loss of HCL during vomiting * Increased excretion of HCO3- in renal malfunction

Question 32

Describe the term acidaemia

Answer 32

•Lower blood pH(body condition known as acidosis)

Question 33

Describe alkalaemia

Answer 33

•The increase of blood pH above the limit(state called alkalosis)

Question 34

List the pH values of some body fluids

Answer 34

.