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Animal Course Physiology Exam > 4.5 Acids, Bases and Buffers > Flashcards

4.5 Acids, Bases and Buffers Flashcards

1
Q
  1. Which of the following statements is CORRECT?
    A. An acid is an electron donor and a base is an electron acceptor.
    B. An acidic solution has a pH less than 7 and a basic solution has a pH greater than 7.
    C. Neutralisation of a strong acid by a strong base gives only water.
    D. The pH of saliva is normally in the range of 8.5–9.5
A

Answer is B: All students should know that pH <7 indicates acidity. Salivary pH is about 6.0–7.4.

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2
Q
  1. Which statement about buffers below is most correct?
    A. A buffer is any acid and base which together control the concentration of pH in the blood.
    B. A buffer is the solution which allows CO2 to be lost from the lungs in order to control the pH of the lungs.
    C. A buffer is a weak base and its acid salt or a weak acid and its basic salt. The ratio of the two components helps maintain blood pH levels.
    D. A buffer is a mixture of two acids which together help to maintain blood pH
A

Answer is C: A buffer has two conjugate components, one dealing with acid, while the other destroys base. Their concentration ratio determines the pH of the solution they are in.

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3
Q
  1. Which of the following statements is FALSE?
    A. An acid is a proton donor and a base is a proton acceptor.
    B. An acidic solution has a pH greater than 7 and a basic solution has a pH less than 7.
    C. Neutralisation of an acid by a base gives a solution of salt in water.
    D. The pH of the stomach is normally in the range of 1.6–1.8.
A

Answer is B: The opposite of this statement is the truth.

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4
Q
  1. Neutralisation of an acid by a base can be represented by the following equation:
    H3O+ + OH- = 2 H2O
    This means that the pH of the solution after the neutralisation is approximately:
    A. 6
    B. 7
    C. 8
    D. 9
A

Answer is B: The solution resulting from a neutralisation reaction should have pH = 7 (should be neutral) – provided that it is properly titrated.

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5
Q
  1. A buffer solution consisting of citric acid and citrate in a ratio of 5: 1 maintains the pH at 7.4. What would be the ratio of the two components if the pH were to become 6.4
    A. 6:1 B. 10:1 C. 50:1 D. 1:10
A

Answer is C: As the ratio of the two components changes, so does the pH of the solution. As pH is a logarithmic scale, a pH value change by 1.0 requires a change of one of the components by a factor of 10. This is achieved if the ratio changes from 5 to 1, to 50 to 1. Furthermore, as the citric acid component has been increased, the pH decreases to be more acidic.

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6
Q
  1. Which of the following statements is closest to a correct definition of an acid?
    A. A substance that ionises in a solution to produce hydronium and hydroxide ions
    B. A substance that reacts with water to produce hydroxide ions
    C. A substance that dissociates in water to produce a solution with pH greater
    than 7.0
    D. A substance that reacts partly with water to produce a low concentration of
    hydronium ions
A

Answer is D: An acid produces hydronium ions (H3O+) when added to water. If the concentration of hydronium ions produced is low, then the acid is a weak acid.

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7
Q
  1. What does the pH of a buffered solution depend on?
    A. The ratio of the components of the buffer solution
    B. The amount of acid added to the buffer
    solution
    C. The amount of base added to the buffer solution
    D. The amount of acid and of base added to the solution
A

Answer is A: The pH of the buffered solution will change very little when either acid or base is added.

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8
Q
  1. What is the long-term acid-base balance in the body controlled by?
    A. The phosphate and carbonic acid/bicarbonate buffers in the blood
    B. The kidneys and the lungs
    C. The phosphate, carbonic acid/bicarbonate and protein buffers in the blood
    and cells
    D. The kidneys
A

Answer is B: Buffers temporarily manage the pH in the body’s liquids. It is from both the lungs and kidneys that acid is excreted (or not) from the body.

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9
Q
  1. You have a bottle of a strong acid and you add 100 ml of this to 1 L of water. What would the pH of this final solution most likely be?
    A. pH = 1
    B. pH = 5
    C. pH = 7
    D. pH = 11
A

Answer is A: Strong acid produces a high concentration of hydronium ions in aqueous solution, so the pH would be low.

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10
Q
  1. What is the approximate range of pH of gastric juice in the stomach?
    A. 1.6–1.8
    B. 6.2–7.4
    C. 7.3–7.5
    D. 7.8–8.6
A

Answer is A: The stomach has the lowest pH in the body due to the secretion of hydrochloric acid (a strong acid) into it.

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11
Q
  1. A buffer solution consisting of acetic acid and acetate ions (base) in a ratio of acid to base of 1:20 maintains the pH at 7.4. What is the ratio of the two components if the pH were to become 8.4 after addition of more of the basic component?
    A. 1:200
    B. 1:21
    C. 1:30
    D. 1:40
A

Answer is A: As pH is a logarithmic scale, a rise in pH value by 1.0 (from 7.4 to 8.4) requires a change in the concentration of the basic component by a factor of 10. This is achieved if the ratio becomes 1–200.

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12
Q
  1. Acidity is stated as a pH value. If the pH of urine sample “A” is 6 and the pH of urine sample “B” is 7, then which of the following is true?
    A. The most acidic sample is sample B.
    B. Sample A has ten times the hydroxide ion concentration of sample B.
    C. The B sample has ten times the hydrogen ion concentration of sample A. D. Sample A has ten times the hydrogen ion concentration of sample B.
A

Answer is D: The solution with higher hydrogen ion (= hydronium ion) concentration has the lower pH.

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13
Q
  1. One form of acid-base imbalance in the body is called acidosis. In this situation, which of the following is true?
    A. The blood is less alkaline than it should be.
    B. The blood’s pH is less than 7.0
    C. The blood is less acidic than it should be.
    D. The concentration of hydrogen ions in the blood is less than it should be.
A

Answer is A: Acidosis = blood pH <7.35. Blood pH less than 7.0 is extremely rare and presages imminent death.

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14
Q
  1. One of the buffer systems in the blood is the carbonic acid/bicarbonate buffer. It helps to maintain the body’s acid-base balance by destroying any excess:
    A. Hydrogen ions in the blood
    B. Acid or base in the blood
    C. Hydroxide ions formed in the blood
    D. Bicarbonate ions formed in the blood
A

Answer is B: A buffer has the ability to destroy either acid or base.

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15
Q
  1. The major buffer system in the extracellular compartment is the:
    A. The protein buffer
    B. Carbonic acid/ bicarbonate buffer
    C. Ammonia buffer
    D. Phosphate buffer
A

Answer is B: “Extracellular compartment” is almost synonymous with blood. The protein buffer is important within cells. The ammonia buffer is important in the kidney’s filtrate.

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16
Q
  1. If a patient was suffering from “acidosis”, what would this mean?
    A. Blood pH is not sufficiently alkaline.
    B. Blood pH is acidic.
    C. There is too little hydronium ion in the plasma.
    D. Blood pH is too acidic.
A

Answer is A: Healthy blood is slightly alkaline. Acidosis is applied to blood with pH below the normal range of 7.35–7.45. If blood has pH <7.35, it is not sufficiently alkaline.

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17
Q
  1. What happens when an acid is added to a buffered solution?
    A. The solution becomes acidic
    B. The pH of the solution decreases significantly.
    C. The pH of the solution decreases very slightly. D. The pH of the solution increases slightly.
A

Answer is C: A buffer will resist change to its pH. But pH does alter very slightly as the basic component destroys the added acid and in the process becomes its cognate partner. This changes the ratio of the two components of the buffer slightly and hence the pH.

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18
Q
  1. Which of the statements below is correct?
    A. The dihydrogen phosphate component of the phosphate buffer releases hydrogen ions into the lungs for excretion and in the process, reverts to monohydrogen phosphate.
    B. Haemoglobin as it passes through the lungs, releases hydronium ions, which are breathed out.
    C. Carbon dioxide that is dissolved in blood diffuses into the alveoli and is breathed out.
    D. Hydronium ions react with bicarbonate ions to form carbonic acid which moves into the lungs for exhalation.
A

Answer is C: Carbon dioxide that we breathe out enters the alveoli after diffusing there from the blood plasma. No other gas is excreted.

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19
Q
  1. When aspirin (an acid) is in the stomach (an acidic environment), what may be said of the aspirin molecules?
    A. Most molecules will be un-ionised and therefore able to be pass through the stomach mucosa.
    B. Most molecules will be ionised and therefore able to be pass through the stomach mucosa.
    C. Most molecules will be un-ionised and therefore NOT able to pass through the stomach mucosa.
    D. Aspirin will be in the form of its salt and therefore able to be pass through the stomach mucosa.
A

Answer is A: Aspirin in an acidic environment will be in its molecular form (and un-ionised). This makes it soluble in non-polar media like the plasma membrane (which is lipid). Being soluble in lipid, molecular aspirin is able to be absorbed from the stomach.

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20
Q
  1. Which statement below best describes an acid solution? The pH is less than:
    A. 5
    B. 6
    C. 7
    D. 8
A

Answer is C: An acidic solution has a pH of less than 7.0

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21
Q
  1. If a patient has blood pH that is 7.3 (which is below the healthy range of blood pH values), which of the following is a correct statement?
    A. The patient has alkalosis.
    B. The patient has excessive alkali.
    C. The patient has acidosis.
    D. The patient has insufficient acid.
A

Answer is C: A pH lower than the healthy blood pH range is called acidosis.

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22
Q
  1. Which of the following mechanisms results in acid being excreted from the body?
    A. Breathing out H PO − (dihydrogen phosphate) from the lungs 24
    B. Excreting HCO − in the urine 3
    C. Excreting NH3 (ammonia) in the urine D. Breathing out CO2 from the lungs
A

Answer is D: As CO2 exhaled from the lungs, carbonic acid in the blood converts into carbon dioxide and water. So as carbon dioxide is exhaled, the amount of carbonic acid within the body decreases.

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23
Q
  1. If the pH of a patient’s blood is 7.4, then it can be said that the patient has:
    A. Acidic blood
    B. Alkaline blood
    C. Neutral blood
    D. Alkalosis
A

Answer is B: pH above 7.0 indicates an alkaline solution. However 7.4 is within the healthy range, so there is no alkalosis.

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24
Q
  1. Which of the following would happen when hydrochloric acid is added to water?
    A. The acid would react with water to from a low concentration of hydronium ions.
    B. The acid would react with water to from a high concentration of hydroxide ions.
    C. The acid would react with water to from a high concentration of hydronium ions.
    D. The acid would react with water to from a high concentration of bicarbonate ions.
A

Answer is C: HCl is a strong acid. Hence a high concentration of hydronium ions would be produced.

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25
Q
  1. If the pH of the stomach contents changed from 3 to 2, which of the following is true?
    A. At pH 2, the concentration of hydronium ions is two thirds of the concentra- tion at pH 3.
    B. At pH 3, the concentration of hydronium ions is 50% more than the concen- tration at pH 2.
    C. At pH 2, the concentration of hydronium ions is ten times the concentration at pH 3.
    D. At pH 3, the concentration of hydronium ions is ten times the concentration at pH 2.
A

Answer is C: When pH decreases from 3 to 2, this indicates an increase in hydro- nium ion concentration by a factor of 10. Remember pH is a logarithmic scale.

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26
Q
  1. The carbonic acid and bicarbonate buffer system is one if the buffers that help to maintain the blood’s pH within the healthy range by doing which of the following?
    A. Carbonic acid destroys excess base in the blood, while bicarbonate destroys excess acid.
    B. Carbonic acid destroys excess acid in the blood, while bicarbonate destroys excess base.
    C. Carbonic acid and bicarbonate destroy excess acid.
    D. Carbonic acid and bicarbonate destroy excess base.
A

Answer is A: A buffer has two components. One is capable of destroying acid, while the other is capable of destroying base.

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27
Q
  1. In a solution like blood that is buffered to minimise changes in pH, what determines the pH of the solution?
    A. The concentration of the hydronium ions
    B. The logarithm of the concentration of the hydronium ions
    C. The ratio of the concentration of hydronium ions to hydroxide ions
    D. The ratio of the concentrations of the two components of the buffer
A

Answer is D: Any hydronium and hydroxide ions present will react with one of the two components of the buffer. So the amount of buffer component (viz. their ratio) governs the concentration of these ions and hence the pH of the solution.

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28
Q
  1. When in solution, an acidic drug also exists as its salt. What feature does the salt of a drug have that may not be shared by the acid form of the drug?
    A. The salt of the drug does not carry an electrical charge but the acid form does.
    B. The salt of the drug may be more soluble in lipid than the acid form of the drug.
    C. The acid form of the drug is ionised, whereas the salt is not.
    D. The salt of the drug may be more soluble in water than the acid form of the
    drug.
A

Answer is D: The salt of the drug, being ionised, is more soluble in water (a polar liquid) than is the drug molecule.

29
Q
  1. Which one of the following best defines an acid?
    A. An aqueous solution with a pH of less than 7.0
    B. A substance that reacts with water to produce hydrogen ions C. A substance that reacts with water to produce hydroxide ions D. A substance that reacts with water to produce hydronium ions
A

Answer is D: A “hydrogen ion” H+ is a bare proton which, if it freely exists, would attach to a water molecule to form the hydronium ion (H3O+). So choice D is a better answer than Choice B.

30
Q
  1. Which one of the following acids is not normally found in the body?
    A. Hydrochloric acid
    B. Carbonic acid
    C. Nucleic acid
    D. Acetylsalicylic acid
A

Answer is D: Acetylsalicylic acid is the medicine known as aspirin.

31
Q
  1. If a sample of blood has a pH of 7.25, which of the following is true?
    A. It is in the healthy range.
    B. It is neutral.
    C. It is acidic.
    D. It is basic.
A

Answer is D: pH above 7.0 indicates basic. 7.25 is below the healthy range.

32
Q
  1. If a blood sample has a pH of 7.25, which of the following is NOT true?
    A. The blood is acidic.
    B. The person may be suffering from metabolic acidosis.
    C. The person may be suffering from respiratory acidosis.
    D. The blood is alkaline.
A

Answer is A: pH must be less than 7.0 for acidic to be true. The condition certainly is an acidosis.

33
Q
  1. Why does drinking acidic solutions such as orange juice NOT make the blood acidic?
    A. Blood is alkaline and alkaline solutions react with ingested acids to neutral- ise them.
    B. The volume of water in the body is great enough that the effect of ingested acidic food and drink on pH is negligible.
    C. The blood has buffers whose components are able to resist changes to blood pH.
    D. The kidney is able to rapidly filter acidic components from blood to avoid pH changes.
A

Answer is C: The blood has the ability to buffer normal intakes of acidic or basic substances. So excursions of blood pH outside the healthy range are prevented.

34
Q
  1. Which statement about the phosphate buffer is correct?
    A. H2 PO4 2− destroys acid and HPO4 − destroys base.
    B. H2 PO4 2− destroys base and HPO4 − destroys acid.
    C. H2 PO4 2− is basic and HPO4 − is acidic.
    D. The ratio of H2 PO4 2−: HPO4 − decreases following the addition of acid.
A

Answer is B: Dihydrogen phosphate is able to destroy base by donating one of its hydrogen atoms (and in the process it becomes monohydrogen phosphate). Choice D is wrong as addition of acid would decrease the proportion of monohydrogen phosphate while increasing dihydrogen phosphate. This would make the ratio increase, that is, the “fraction” would be larger.

35
Q
  1. If the pH of a sample of blood was 7.4, which term below would be applied to it?
    A. Acidotic
    B. Acidic
    C. Alkalotic
    D. Alkaline
A

Answer is D: 7.4 is in the healthy range for blood. Being greater than 7.0 indicates alkaline.

36
Q
  1. Three of the solutions below have the SAME level of acidity (or alkalinity); the other is different. Which is the different one?
    A. Blood
    B. A neutral solution
    C. A solution with pH = 7
    D. A solution with a hydrogen ion concentration of 10−7 mol/L
A

Answer is A: Blood has pH in the range 7.35–7.45. The other choices all have pH = 7.0

37
Q
  1. Which of the following statements is a definition of a buffer solution?
    A. One where the number of osmoles of solute equals the number of moles
    B. One where the concentration of hydronium ions equals the concentration of
    hydroxide ions
    C. A solution that resists change to its pH
    D. A solution that reacts partly with water to produce a relatively low concentration of hydronium ions
A

Answer is C: This is a definition of a buffer solution. Choice B indicates a neutral solution, while choice D alludes to a weak acid.

38
Q
  1. Which of the following solutions is the most acidic?
    A. Blood plasma
    B. Gastric juice
    C. A solution with pH = 7
    D. A solution with hydronium ions at a concentration of 10−5 mol/L
A

Answer is B: Gastric juice has a pH of about 1.5. The solution in choice D has a pH of 5 (= negative log of 10−5) .

39
Q
  1. Pure water contains small but equal amounts of hydronium (H3O+) ions and hydroxide (OH−) ions. This means that water is:
    A. Acidic
    B. Basic
    C. Acidic and basic
    D. Neither acidic nor basic
A

Answer is D: When the concentrations of hydronium and hydroxide ions are the same, their effects are cancelled, and the solution is neutral.

40
Q
  1. What do we call a substance that when added to water, reacts with water to produce hydronium ions?
    A. An ionic compound B. A base
    C. An electrolyte
    D. An acid
A

Answer is D: This is a definition of an acid.

41
Q
  1. How does the blood’s phosphate buffer behave when a hydronium ion is encountered?
    A. HPO4 2− destroys the hydronium ion and becomes H2 PO4 −, and blood pH
    decreases very slightly.
    B. H2 PO4 − destroys the hydronium ion and becomes HPO4 2−, and blood pH decreases very slightly.
    C. HPO4 2− destroys the hydronium ion and becomes HPO4 −, and blood pH increases very slightly.
    D. HPO4 2 − destroys the hydronium ion and becomes HPO4 2−, and blood pH increases very slightly.
A

Answer is A: Monohydrogen phosphate is the species that destroys acid (by accepting a hydrogen ion from the acid). Blood pH would decrease very slightly as the concentration of monohydrogen phosphate decreases slightly and the concentration of dihydrogen phosphate increases slightly.

42
Q
  1. One of the statements below about buffers is correct. Which one?
    A. A buffer consists of an acid and a base.
    B. A buffer will react with water to produce hydronium ions.
    C. A solution that is neither acidic nor basic is called a buffer.
    D. The components of a buffer are conjugate pairs.
A

Answer is D: A buffer has two components. Each component converts to the other as it destroys acid (or base). Choice A is incorrect as a buffer is a weak acid and its slightly basic salt (or vice versa).

43
Q
  1. An acid may be defined as a substance that:
    A. Reacts completely with water producing a high concentration of hydronium ions
    B. Reacts with water to produce hydroxide ions
    C. Produces a pH of more than seven when in solution
    D. Reacts with water to produce hydronium ions
A

Answer is D: An acid produces hydronium ions. Choice A defines a strong acid (but not a weak one).

44
Q
  1. One of the statements below about buffers is WRONG. Which one?
    A. A buffer consists of a weak acid and its slightly basic salt.
    B. A buffer will react with water to produce hydronium ions.
    C. A solution that resists change to its pH is called a buffer.
    D. The components of a buffer are conjugate pairs.
A

Answer is B: The ability to produce hydronium ions with water defines an acid, not a buffer.

45
Q
  1. An acid may be defined by which one of the following statements?
    A. A substance with equal concentrations of hydronium and hydroxide ions B. A substance that reacts partly with water to produce hydronium ions
    C. A substance that maintains the pH of the solution it is in
    D. A substance that reacts with water producing hydroxide ions
A

Answer is B: This is a definition of an acid.

46
Q
  1. Which of the following defines an acid?
    A. When in solution, resists change to pH
    B. Reacts with water to produce hydronium ions
    C. Reacts with a buffer to produce water
    D. Has a pH of more than 7
A

Answer is B: This is a definition of an acid. All other choices are wrong statements.

47
Q
  1. Which of the following is NOT an acid?
    A. A solution having a pH of 3
    B. A substance which reacts with water to produce hydronium ions C. Carbonic acid
    D. A solution that resists change to its pH
A

Answer is D: Such a solution is a buffer.

48
Q
  1. What effect would a base have when added to the following solutions?
    A. Tap water – it would react to produce hydronium ions.
    B. Tap water – it would react to produce hydroxide ions.
    C. Buffered water – it would raise the pH of the solution.
    D. Unbuffered water – it would lower the pH of the solution.
A

Answer is B: A base has the ability to produce hydroxide ions when added to water.

49
Q
  1. What effect would an acid have when added to the following solutions?
    A. Tap water – it would react to produce hydronium ions.
    B. Tap water – it would react to produce hydroxide ions.
    C. Buffered water – it would lower the pH of the solution.
    D. Unbuffered water – it would raise the pH of the solution.
A

Answer is A: An acid has the ability to produce hydronium ions when added to water.

50
Q
  1. A fresh sample of blood (a buffered solution) is withdrawn from the body and its pH measured at 7.4. A small quantity of strong acid (as an isotonic solution) is added to it. Which of the following values is most likely to be the pH of the resulting blood solution?
    A. 3.0
    B. 7.3
    C. 7.4
    D. 7.5
A

Answer is C: Blood is buffered, so very little pH change will result from the addition of acid. Certainly it is not enough to change the pH by 0.1.

51
Q
  1. Blood in the body is different to a buffered solution held in a beaker. This is because hydronium (hydrogen) ions can be removed from solution in blood almost immediately by:
    A. Filtration in the kidney from where it is eliminated from the body in urine
    B. Combining with hydroxide ions to form water which is eliminated as urine
    C. Combining with bicarbonate to form carbonic acid which disassociates to water and carbon dioxide which is breathed out
    D. Reacting with monohydrogen phosphate to form dihydrogen phosphate
A

Answer is C: This is the best answer as it describes the buffer action and the continuous nature of exhalation mean that there is no delay in excreting carbon dioxide. Choice A is also correct, but the elimination of acid via kidneys is not immediate.

52
Q
  1. The definition of an acid is a substance that reacts:
    A. Completely with water to produce a large concentration of hydronium ions
    B. With water to produce hydroxide ions
    C. With a base to produce a neutral salt
    D. With water to produce hydronium ions
A

Answer is D: This is the best answer. Choice A is true of a strong acid only. Choice C is incorrect as the salt produced may also be basic or acidic.

53
Q
  1. Choose the INCORRECT statement about buffer solutions.
    A. The pH of a buffer does not change on addition of acid or base.
    B. A buffer has two components which may be a weak acid and its salt.
    C. A buffer has two components which may be a weak base and its salt.
    D. pH of a buffer depends only on the ratio of its components.
A

Answer is A: The pH of a buffer does change, albeit very slightly, on addition of acid or base.

54
Q
  1. In the condition known as acidosis, the blood pH would be:
    A. Greater than 7.45.
    B. Less than 7.45.
    C. Less than 7.35.
    D. Less than 7.00.
A

Answer is C: The healthy pH range for blood is 7.35–7.45. A pH value below this, while still alkaline, indicates insufficient alkalinity (or too much acidity) and is termed acidosis.

55
Q
  1. As the blood becomes more acidic, hydrogen (hydronium) ions combine with bicarbonate ions to form carbonic acid which in turn dissociates into carbon dioxide (to be breathed out by the lungs) and water. Which is the equation describing this reaction?
    A. CO2 + H2O ← H2CO3 ← H+ + HCO3 −
    B. CO2 + H2O → H2CO3 → H+ + HCO −
    C. CO2 + H2O ← H+ + HCO − ← H2CO3
    D. H+ + HCO3 − ← CO2 + H2O ← H2CO3
A

Answer is A: Choice B is going in the wrong direction, while choices C and D are scrambled.

56
Q
  1. A buffer solution consisting of H2 PO4 − (acid) and HPO4 2− (base), in a ratio of
    1:4, maintains the pH at 7.4. What is the ratio of these two components if the pH were to become 8.4 after the addition of more of the basic component of the buffer?
    A. 1:5
    B. 2:4
    C. 1:8
    D. 1:40
A

Answer is D: The pH of a buffer is determined by the ratio of its two components. pH is a logarithmic scale of the hydronium ion concentration of a solution. Hence the ratio must change by a factor of 10 in order for the pH to change by one (i.e. change from 7.4 to 8.4).

57
Q
  1. Which of the following pH values would you expect to a dilute solution of a weak base to have?
    A. 2.4
    B. 6.2
    C. 8.2
    D. 12.4
A

Answer is C: A base has a pH greater than 7.0. A weak base will have a value that is not much greater than 7.0

58
Q
  1. A buffer solution having a pH of 8.5 has a small amount of strong acid added to it. What is its pH value likely to be closest to?
    A. 5.0
    B. 8.4
    C. 8.6
    D. 12.4
A

Answer is B: A buffer solution resists change to its pH. This means that its pH will change very little, but it will change slightly. As acid has been added, its pH will drop by a small amount.

59
Q
  1. Which of the following statements about the role of the kidneys or lungs in the maintenance of acid-base balance within the body is FALSE?
    A. The kidneys are able to affect several buffer systems but the lungs affect only one.
    B. The lungs exert their influence on the carbonic acid/bicarbonate buffer system.
    C. Neither the lungs nor the kidneys have much influence over the protein buffer.
    D. The kidneys are able to respond more rapidly than the lungs to changes in acid-base balance.
A

Answer is D: The lungs with each breath are able to excrete acid, by exhaling CO2. So the lungs are able to respond more rapidly than the kidneys.

60
Q
  1. A buffered solution is able to resist change to its pH when an acid is added to the solution by doing which of the following?
    A. Removing hydrogen ions from the solution
    B. Removing hydroxide ions from the solution
    C. Removing hydrogen peroxide from the solution
    D. Removing hydronium ions from the solution
A

Answer is D: A buffered solution contains two entities, one of which can remove hydronium ions from solution, turning them into water. Sometimes “hydrogen ions” is used instead of the more correct hydronium ions. Hydrogen peroxide is not produced by adding acid to a solution.

61
Q

61.The healthy range for blood pH is from 7.35 to 7.45. To what blood pH does the term “acidosis” refer?
A. pH greater than 7.45 B. pH less than 7.35
C. pH below 7.00
D. pH above 7.00

A

Answer is B: Acidosis refers to any blood pH below the lower limit of normal which is 7.35.

62
Q
  1. To what blood pH does the term “alkalosis” refer?
    A. pH greater than 7.45 B. pH less than 7.35
    C. pH below 7.00
    D. pH above 7.00
A

Answer is A: Alkalosis refers to any blood pH above the upper limit of normal which is 7.45.

63
Q
  1. Which body fluid is at the lowest pH?
    A. Urine
    B. The contents of the duodenum
    C. Blood
    D. The contents of the stomach
A

Answer is D: Acids have low pH (less than 7). The stomach contents contain hydro- chloric acid secreted by the parietal cells of the gastric glands so typically has a pH of less than 2.0. Urine, while usually acidic, rarely falls below pH of 5.

64
Q
  1. Which of the following reactions demonstrates the action of the ammonia (NH3) buffer?
    A. H3O+ + NH4+ → H2O + NH3
    B. H3O+ + NH3 → H2O + NH4+
    C. H2O + NH3 → H3O+ + NH4+
    D. H2O + NH4+ → H3O+ + NH3
A

Answer is B: A buffer must destroy acid, so choices C and D, in which acid is “created”, are wrong. A buffer destroys acid by accepting a hydrogen atom from the hydronium molecule so converting it to water: choice B describes this and has equal numbers of hydrogen atoms (6) on each side of the arrow, while choice A has an imbalance of H atoms and of charge.

65
Q
  1. Which reaction below demonstrates the action of the bicarbonate buffer?
    A. H3O+ + HCO3 − → H2O + H2CO3
    B. H3O+ + H2CO3 → H2O + HCO3 −
    C. H2O + HCO3 − → H3O+ + H2CO3
    D. H2O + H2CO3 → H3O+ + HCO3 −
A

Answer is A: A buffer must destroy acid, so choices C and D, in which acid is “created”, are wrong. A chemical reaction must have equal numbers of H atoms on each side of the arrow, but choice B has 5H on one side and 3H on the other.

66
Q
  1. Which reaction below demonstrates the action of the phosphate buffer?
    A. H2O + HPO4 2− → H3O+ + H2PO4 −
    B. H3O+ + H2PO4 − → H2O + HPO4 2−
    C. H3O++ + HPO4 2− → H2O + HPO4 2−
    D. H2O + H2PO4 − → H3O++ + HPO4 2−
A

Answer is C: A buffer must destroy acid, by accepting a hydrogen atom from a hydronium ion and thus converting it to water. This means that monohydrogen phosphate must appear on the left of the arrow and dihydrogen phosphate on the right. So choices B and D are wrong. There must be equal numbers of H atoms (4) on each side of the arrow, but choice B has 5H on one side and 3H on the other.

67
Q
  1. If humans venture to above 5000 m in altitude, hyperventilation (in response to low atmospheric pressure) results in a very low concentration of dissolved CO2 in the blood. What is the consequence of this?
    A. Alkalosis with pH less than 7.3
    B. Acidosis with pH less than 7.3
    C. Alkalosis with pH greater than 7.5
    D. Acidosis with pH greater than 7.5
A

Answer is C: A deficiency of CO2 dissolved in blood will mean that that amount of carbonic acid produced is too low. This will cause blood pH to rise – a condition known as alkalosis.

68
Q
  1. Which of the following is a substance known as a salt?
    A. Potassium chloride
    B. Sodium
    C. Bicarbonate
    D. Lactate
A

Answer is A: A salt is produced when an acid reacts with a base. Hence it has two words in its name: the first comes from the base (potassium hydroxide), while the second word is derived from the name of the acid (hydrochloric acid).

69
Q
  1. “Quick-eze” is an oral antacid tablet that contains calcium carbonate as the active ingredient. It is intended to relieve “indigestion” by neutralising stomach acid. Which equation below represents the neutralisation reaction?
    A. H2O + Ca2+ CO3 2− → Ca2+ Cl 2− + 2HCl + CO
    B. 2HCl + Ca2+CO3 2− → Ca2+ Cl 2− + H2O + CO2
    C. Ca2+ Cl 2− + Ca2+ CO 2− → 2HCl + H2O + CO2
    D. CO2 + 2HCl + Ca2+ Cl 2− → Ca2+ CO3 2− + H2O
A

Answer is B: A neutralisation reaction involve stomach acid (hydrochloric acid) reacting with a base (calcium carbonate is a weak base) to produce a salt (calcium chloride) and water. Choice D is wrong as calcium carbonate does not appear as a reagent.

Animal Course Physiology Exam (15 decks)

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