Anatomy Practice Questions (Acids, Bases, and Buffers) Answer Key

Anatomy Practice Questions (Acids, Bases, and Buffers) 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. Neutralization 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 2. Which statement about buffers below is most correct? a. 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 3. 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. Neutralization 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 4. Neutralization of an acid by a base can be represented by the following equation: H O3 2 OH 2H O + − + → This means that the pH of the solution after the neutralization is approximately: a. 6 b. 7 c. 8 d. 9 5. 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 6. 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 7. The pH of a buffered solution depends 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 8. The long term acid-base balance in the body is 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 9. You have a bottle of a strong acid and you add 100 ml of this to one litre 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 10. 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 11. 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 12. 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 10 times the hydroxide ion concentration of sample B c. The B sample has 10 times the hydrogen ion concentration of sample A d. Sample A has 10 times the hydrogen ion concentration of sample B 13. One form of acid base imbalance in the body is called acidosis. In this situation, which of the following is true? A. 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 14. 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 15. 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 16. 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 17. 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 18. 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 19. When aspirin (an acid) is in the stomach (an acidic environment), what may be said of the aspirin molecules? a. Most molecules will be unionised 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 unionised and therefore NOT able to be 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 20. Which statement below best describes an acid solution? The pH is less than: a. 5 b. 6 c. 7 d. 8 21. 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 22. Which of the following mechanisms results in acid being excreted from the body? a. Breathing out H2PO4 - (dihydrogen-phosphate) from the lungs b. Excreting HCO3 - in the urine c. Excreting NH3 (ammonia) in the urine d. Breathing out CO2 from the lungs 23. 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 24. 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 25. 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 concentration at pH 3 b. at pH 3, the concentration of hydronium ions is 50% more than the concentration 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 26. The carbonic acid and bicarbonate buffer system is one of the buffers that help to maintain the blood’s pH within the healthy range by doing which of the following? a. b. c. d. Carbonic acid destroys excess base in the blood while bicarbonate destroys excess acid Carbonic acid destroys excess acid in the blood while bicarbonate destroys excess base Carbonic acid and bicarbonate destroy excess acid Carbonic acid and bicarbonate destroy excess base 27. 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 28. 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 29. 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 30. 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 31. 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 32. 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 33. Why does drinking acidic solutions such as orange juice NOT make the blood acidic? A. a. Blood is alkaline and alkaline solutions react with ingested acids to neutralise 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 34. Which statement about the phosphate buffer is correct? a. H2PO4 2− destroys acid and HPO4 − destroys base b. H2PO4 2− destroys base and HPO4 − destroys acid c. H2PO4 2− is basic and HPO4 − is acidic d. The ratio of H2PO4 2− : HPO4 − decreases following the addition of acid 35. 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 36. 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 b. A neutral solution c. A solution with pH = 7 d. A solution with a hydrogen ion concentration of 10-7 mol/L 37. 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 38. 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 moles/L 39. 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 40. 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 41. How does the blood’s phosphate buffer behave when an hydronium ion is encountered? a. HPO4 2− destroys the hydronium ion and becomes H2PO4 - – and blood pH decreases very slightly b. H2PO4 - destroys the hydronium ion and becomes HPO4 2− and blood pH decreases very slightly c. HPO4 2− destroys the hydronium ion and becomes H2PO4 - and blood pH increases very slightly d. H2PO4 - destroys the hydronium ion and becomes HPO4 2− and blood pH increases very slightly 42. 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 43. 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 7 when in solution d. reacts with water to produce hydronium ions 44. 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 45. 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 46. Which of the following defines an acid? a. b. c. d. when in solution, resists change to pH reacts with water to produce hydronium ions reacts with a buffer to produce water has a pH of more than 7 47. 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 48. 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. Un-buffered water: – it would lower the pH of the solution 49. 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. Un-buffered water: it would raise the pH of the solution 50. 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 51. 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 dissociates to water and carbon dioxide which is breathed out d. Reacting with mono-hydrogen phosphate to form di-hydrogen phosphate 52. 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 53. 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 54. 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 55. 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 2 + ← H O H C2 3 O H ← +HCO3 + − b. CO2 2 + → H O H C2 3 O H → +HCO3 + − c. CO2 2 + ← H O H H+ ← CO3 2 H CO3 + − d. H HCO CO H O H CO + − + ←3 2 + ← 2 2 3 56. A buffer solution consisting of H2PO4 − (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 57. Which of the following pH values would you expect a dilute solution of a weak base to have? a. 2.4 b. 6.2 c. 8.2 d. 12.4 58. 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 59. 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.