Buffers

Question 1

Identity two uses of buffers in industry or medicine

Answer 1

1. Buffers are used in antacid tablets, and aspirin may contain a buffering agent, to maintain the pH of aspirin as it passes through the acidic stomach.
2. KPO4 is used in fertilizer as pH fluctuations can cause loss of nitrogen.

Question 2

Explain the importance of buffers in organisms.

Answer 2

Control is essential in living organisms. A high hydrogen ion concentration slows down energy production in cells, and interferes in the functioning of calcium ions.

Question 3

Account for the role of buffers when using a pH meter.

Answer 3

Buffers are used to calibrate pH meters, which must be kept in the buffer solution and not allowed to dry out. The buffer solution maintains its pH and can be used to set the probe to a correct, set value.

Question 4

Explain the buffering action of blood.
(add equations later)

Answer 4

Blood is a buffering solution, containing H2CO3 (aq)/HCO3-, which needs a pH around 7.4. CO2 dissolves in the blood, forming carbonic acid (weak acid) that ionises to form the hydrogen carbonate ion.

Question 5

What is H2CO3?

Answer 5

Carbonic acid

Question 6

What is HCO3?

Answer 6

Bicarbonate (sodium - spectator)

Question 7

A student starts to hyperventilate. The teacher asks her to breathe in and out of a paper bag. Explain how the treatment works.
(also add in equations)

Answer 7

A hyperventilating student has a blood pH of 7.6. Exhaled air contains more CO2, as such the carbon dioxide breathed in will dissolve in the blood plasma forming carbonic acid - producing hydrogen and bicarbonate ions. Extra hydrogen ions increase the acidity of her blood, reducing the change in her ph.

Question 8

Explain with reference to a chemical principle of how blood is able to buffer.

Answer 8

1. Chemical equations
2. f the blood is acidic ([H+] increases), the equilibrium shifts to the left to use hydrogen excess ions, as per LCP. If a base is added, the eq. shifts right to produce hydrogen ions

Question 9

Why does blood buffering work?

Answer 9

Fundamentally, carbonic acid is a weak acid, so any increase or decrease in the amount of acid present will produce a small change in the hydro. conc., thus a small change in pH will occur.

Question 10

What is the equations for equilibrium that i should memorise?

Answer 10

CO2 (g) + H2O (l) <–> H2CO3 (aq)
H2CO3 (aq) <—> H+ + HCO3- (aq)

Question 11

What is the random fact that i need to memorise?

Answer 11

pKa = pH

Question 12

Why would acetic acid alone is not an effective buffer solution?

Answer 12

1. Should have equimolar/comparable amounts of weak sub. and its conjugate.
2. An increase in pH can be counteracted by shifting the eq. to minimise the change
3. The reverse situaiton can not counteracted, as the conc. of acetic ions on the products is too low.

Question 13

What is a buffer?

Answer 13

A solution consisting of approximately equimolar amounts of weak acid or base, and its conjugate. Its role is as a solution to resist small changes in pH

Question 14

What is the fundamental last mark of a buffer response?

Answer 14

Link the changes in conc. of H3)+ and OH- to the buffer’s ability to resist small changes in pH (throw in the formula if u really want to - pH= -log[H3O+])