4.3 Diffusion and Osmosis

Question 1

1. Consider two aqueous solutions of different concentration separated by a semi- permeable membrane. In this situation, osmosis results in:
   A. Water molecules moving to the side where the solution concentration is lower
   B. The more concentrated solution becoming even more concentrated
   C. The more dilute solution becoming even more dilute
   D. The more concentrated solution becoming more dilute

Answer 1

Answer is D: The result of osmosis is that the more concentrated solution becomes more dilute.

Question 2

2. Osmosis may be defined as which of the following?
   A. The diffusion of water molecules across a semipermeable membrane from the solution with lower water concentration into the solution of higher water concentration
   B. The movement of water molecules across a semipermeable membrane from the solution of higher concentration into the solution of lower concentration
   C. The diffusion of solute particles across a semipermeable membrane from the
   solution of higher concentration into the solution of lower concentration
   D. The movement of water molecules across a semipermeable membrane from the solution of lower concentration into the solution of higher concentration

Answer 2

Answer is D: The definition should include “water”, movement through an SP membrane and direction of water flow from more dilute solution into the solution of higher concentration.

Question 3

3. What is the movement of water molecules across a plasma membrane from the side where the solution concentration is more dilute to the side where the solu- tion is more concentrated called?
   A. Osmosis
   B. Reverse osmosis
   C. Diffusion
   D. Hydration

Answer 3

Answer is A: Osmosis is the diffusion of WATER molecules through a membrane, from where there is a higher concentration of water molecules to where there is a lower concentration of water molecules (i.e. into the more concentrated solution).

Question 4

4. The movement of water molecules through a plasma membrane from the side where there is a higher concentration of water molecules to the side where there are fewer is best known as:
   A. Diffusion
   B. Osmosis
   C. Pinocytosis
   D. Hydrolysis

Answer 4

Answer is B: Osmosis is the diffusion of water molecules through a membrane, down to their concentration gradient.

Question 5

5. The diffusion of water molecules across a cell membrane from the side where the solution concentration is more dilute to the side where it is greater is known as which of the following?
   A. Osmosis
   B. Filtration
   C. Hydrolysis
   D. Buffer action

Answer 5

Answer is A: This is a definition of osmosis.

Question 6

6. If a semipermeable membrane separates two aqueous solutions with different osmotic pressures, what will be the direction of water flow between solutions? From:
   A. Higher osmotic pressure to the solution of lower osmotic pressure
   B. Lower osmotic pressure to the solution of higher osmotic pressure
   C. Higher concentration to the solution of lower concentration
   D. Higher hydrostatic pressure to the solution of lower hydrostatic pressure

Answer 6

Answer is B: Lower osmotic pressure means a lower solution concentration (and a higher concentration of water molecules). Water moves from the dilute solution into the more concentrated one.

Question 7

7. During dialysis, what moves across a semipermeable membrane (and how)?
   A. Water molecules by diffusion from the region of high solute concentration to the region of low solute concentration
   B. Water molecules by filtration from the region of high hydrostatic pressure to the region of low hydrostatic pressure
   C. Solutes by diffusion from the region of high solute concentration to the region of low solute concentration
   D. Solutes by filtration from the region of low hydrostatic pressure to the region of high hydrostatic pressure

Answer 7

Answer is C: Dialysis refers to movement of solutes (not water). Choice D is wrong as filtration refers to movement due to hydrostatic pressure difference from the solution under higher pressure to low pressure.

Question 8

8. A suitable definition of osmosis would be movement:
   A. Of solute particles through a plasma membrane from the side where their concentration is greatest to the side where it is lower
   B. Of water molecules through a plasma membrane from the side where their concentration is greatest to the side where it is lower
   C. Of a substance from a region where it is in high concentration to where its concentration is lower
   D. Caused by a hydrostatic pressure difference

Answer 8

Answer is B: Osmosis refers to movement of water molecules (not other molecules), by diffusion.

Question 9

9. The difference between dialysis and diffusion is that:
   A. Dialysis involves the movement of water molecules.
   B. Diffusion involves movement against the concentration gradient.
   C. Dialysis involves passive movement through a cell membrane. D. Diffusion is caused by a hydrostatic pressure difference.

Answer 9

Answer is C: Diffusion is passive and occurs in the direction of the concentration gradient. Diffusion can occur within a solution or across a membrane. Dialysis, on the other hand, requires a membrane and is a term applied to solutes, not water molecules.

Question 10

10. Osmosis involves the movement of:
    A. Water molecules through a membrane from a region of higher concentra- tion of water molecules to a region of lower water molecule concentration
    B. Solute particles from a region of higher solution concentration to a region of lower solution concentration
    C. Water molecules from a region of lower concentration of water to a region of higher water molecule concentration
    D. Solute particles through a membrane from a region of lower solute concentration to a region of higher solute concentration

Answer 10

Answer is A: Osmosis involves water molecules (not solutes) moving down their concentration gradient into a solution of lower concentration of water molecules.

Question 11

11. What does “osmosis” refer to?
    A. The constant random motion of ions and molecules
    B. The movement of ions and molecules from regions of high concentration to
    regions of low concentration
    C. The movement of water molecules through a semipermeable membrane
    D. The movement of water molecules through a semipermeable membrane
    from the side with higher water concentration to the side with lower water concentration

Answer 11

Answer is D: The definition must include water molecules, crossing an SP membrane and a correct direction of movement.

Question 12

12. What is the difference between filtration and diffusion?
    A. Diffusion can occur through a biological membrane, whereas filtration cannot.
    B. Filtration can occur through a biological membrane, whereas diffusion cannot.
    C. Filtration is the movement of molecules caused by a pressure difference, but diffusion does not involve a difference in pressure.
    D. Diffusion is the movement of molecules caused by a pressure difference, but filtration does not involve a difference in pressure.

Answer 12

Answer is C: Filtration requires a pressure difference; diffusion does not. Both diffusion and filtration can occur through a membrane.

Question 13

13. What is the difference between osmosis and dialysis?
    A. Dialysis involves the movement of solute molecules, whereas osmosis refers to water molecules.
    B. Osmosis involves the movement of solute molecules, whereas dialysis refers to water molecules.
    C. Osmosis involves movement of molecules across a membrane, but dialysis does not involve a membrane.
    D. Dialysis involves movement of molecules across a membrane, but osmosis does not involve a membrane.

Answer 13

Answer is A: Osmosis refers to the movement of water molecules (only) through a membrane. Only choice A is consistent with this.

Question 14

14. Which one of the following processes that describe movement of the particles in a solution does NOT require passing through a membrane?
    A. Diffusion
    B. Filtration
    C. Dialysis
    D. Osmosis

Answer 14

Answer is A: While diffusion can occur through a membrane, its presence is not required in order to define diffusion.

Question 15

15. Which statement about the osmotic pressure of an aqueous solution is correct? Osmotic pressure:
    A. Is an indication of the force with which pure water moves into that solution
    B. Is a measure of the tendency of water to move into the solution
    C. Is the drawing power of water and depends on the number of molecules in the solution
    D. Of a solution is called its osmolarity in mosmol/kg

Answer 15

Answer is B: Solutions with high “osmotic pressure” are concentrated solutions, and so water will diffuse into such solutions from solutions of lower concentration – a process known as osmosis. The other answers are nonsense.

Question 16

16. Diffusion is the term given to the process where:
    A. Molecules move along their concentration gradient from high concentration to low concentration.
    B. Water moves along its concentration gradient from low concentration to high concentration.
    C. ATP is used to move ions along their concentration gradient.
    D. A membrane protein, by changing shape after binding to a molecule, moves the molecule across the plasma membrane.

Answer 16

Answer is A: This is the only correct definition of diffusion.

Question 17

17. By what name is the movement of solute particles through a selectively permeable membrane, in the direction of their concentration gradient, known?
    A. Diffusion
    B. Dialysis
    C. Osmosis
    D. Filtration

Answer 17

Answer is B: While the solute particles are indeed diffusing through the membrane, the presence of a membrane makes dialysis the appropriate term to use. Diffusion is also applied to the movement of particles within a solution even when they do not cross a membrane.

Question 18

18. Blood has a slightly higher osmotic pressure than the interstitial fluid that surrounds capillaries. What is the effect of this?
    A. Water will tend to move from the interstitial fluid into the capillaries.
    B. The solution concentration of blood is less than the solution concentration of interstitial fluid.
    C. Water will tend to move from the capillaries into the interstitial fluid.
    D. Capillaries will expand in diameter.

Answer 18

Answer is A: Water will move through a membrane into a solution of higher osmotic pressure (the blood) from a solution of lower osmotic pressure.

Question 19

19. Consider a patient undergoing kidney dialysis, whose blood has bicarbonate at a concentration of 14 mmol/L and urea at 23 mmol/L. The dialysing liquid has bicarbonate at 32 mmol/L and urea at 0 mmol/L. In which direction will these substances flow?
    A. Bicarbonate will flow from patient’s blood to dialysing liquid; urea will flow from patient’s blood into dialysing liquid.
    B. Bicarbonate will flow from dialysing liquid to patient’s blood; urea will flow from dialysing liquid into patient’s blood.
    C. Bicarbonate will flow from dialysing liquid to patient’s blood; urea will flow from patient’s blood into dialysing liquid.
    D. Bicarbonate will flow from patient’s blood to dialysing liquid; urea will flow from dialysing liquid to patient’s blood.

Answer 19

Answer is C: Molecules will flow from areas of high concentration towards areas of low concentration. Hence bicarbonate will flow from the dialysing liquid at 32 to blood at 14 mmol/L, while urea will flow from blood at 23 mmol/L to the dialysing liquid at 0 mmol/L.

Question 20

20. Which is the best description for the osmotic pressure of a solution?
    A. The pressure that needs to be applied to the solution while it is separated from pure water by a membrane, to prevent a net flow of water through the membrane into the solution.
    B. The force with which pure water moves through a membrane into that solution as a result of its solute concentration.
    C. The movement of particles through a membrane, where the movement is caused by a hydrostatic pressure.
    D. It is the force of attraction for water by undissolved particles in the solution.

Answer 20

Answer is A: The application of a hydrostatic pressure to a solution in order to oppose and prevent the osmotic flow of water into that liquid is the basis for assign- ing a value to that solution for its “osmotic pressure”. Osmotic pressure is the value of this externally applied hydrostatic pressure. Choice C describes filtration. Choices B and D are nonsense.

Question 21

21. In which of the following situations would the osmotic pressure of blood be the greatest?
    A. In a patient whose blood osmolarity is 290 mosmol/L
    B. In a patient whose blood osmolarity is 280 mosmol/L and whose urine specific gravity is 1.002
    C. In a patient with hyperthermia
    D. In a patient who is dehydrated

Answer 21

Answer is D: The healthy range for blood osmolarity is 280–300 mosmol/L. A dehydrated person would have a blood osmolarity approaching or exceeding 300 mosmol/L.

Question 22

22. Osmosis involves movement of water from where the:
    A. Water concentration is lower to where it is higher
    B. Solute concentration is higher to where it is lower
    C. Solution is more concentrated to where it is less concentrated
    D. Water concentration is higher to where it is lower

Answer 22

Answer is D: The healthy range for blood osmolarity is 280–300 mosmol/L. A dehydrated person would have a blood osmolarity approaching or exceeding 300 mosmol/L.

Question 23

22. Osmosis involves movement of water from where the:
    A. Water concentration is lower to where it is higher
    B. Solute concentration is higher to where it is lower
    C. Solution is more concentrated to where it is less concentrated
    D. Water concentration is higher to where it is lower

Answer 23

Answer is D: In osmosis water molecules flow down their concentration gradient (and from weaker solutions to more concentrated ones).

Question 24

23. What is “osmotic pressure”?
    A. The pressure exerted by a solution due to its concentration
    B. A measure of solution concentration expressed in the units of pressure
    C. The pressure exerted by the blood colloidal plasma proteins
    D. The pressure that drives water movement out of the arterial end of
    capillaries

Answer 24

Answer is B: Osmotic pressure is a way of expressing solution concentration. The word pressure in the term “osmotic pressure” makes it tempting to erroneously think of the solution exerting some type of pressure due to its solutes.

Question 25

24. If a red blood cell (RBC) is placed in a solution that has a greater concentration than that inside the RBC, what will happen?
    A. The RBC will crenate.
    B. The RBC will haemolyse.
    C. There will be a net movement of water out of the RBC into the solution.
    D. There will be no net movement of water out of the RBC.

Answer 25

Answer is C: Water will flow by osmosis from the RBC into the surrounding solution. If the difference in concentration is large enough, the outflow of water will be large, and the RBC will also shrivel (crenate) as a result of this outflow.

Question 26

25. One of the following is an example of osmosis. Which one?
    A. Water moving from the glomerulus of a nephron into the Bowman’s capsule
    B. Water leaving a blood capillary from close to its arteriole end, to enter the interstitial fluid
    C. Water entering a red blood cell that is in a 0.8% sodium chloride solution, by passing through its plasma membrane
    D. Water evaporating from perspiration on the skin

Answer 26

Answer is C: Osmosis refers to the movement of water through a membrane in the direction of its concentration gradient. A 0.8% solution is hypotonic to the contents of the RBC so water would enter the cell. In both choice A and C, the water is mov- ing due to a hydrostatic pressure difference.

Question 27

26. The Na+/K+ ATPase pump in the plasma membrane moves Na out of the cell and K into the cell against their concentration gradient. Then Na re-enters the cell and K leaks out of the cell, along their concentration gradients through their membrane channels. What is the movement of Na and K along their concentration gradients called?
    A. Active transport
    B. Diffusion
    C. Facilitated diffusion
    D. Osmosis

Answer 27

Answer is B: The movement of these ions down their concentration gradient is dif- fusion. The concentration gradient is produced by the active transport of the Na+/ K+ ATPase pump.

Question 28

27. Which of the following statements is FALSE?
    A. Filtration is movement of water caused by a difference in hydrostatic pres- sure, while diffusion results from a difference in concentration.
    B. Both diffusion and filtration will tend to continue till there is an equal amount on both sides of the membrane.
    C. Any hypertonic solution has a concentration lower than that of blood, while a hypotonic solution has a concentration greater than the blood.
    D. Water moves into a red blood cell resulting in haemolysis and out of a cell by a process called plasmolysis.

Answer 28

Answer is C: Hypertonic solutions have a concentration greater than blood. Plasmolysis is the process in which cells lose water in a hypertonic solution.

Question 29

28. Which of the following may happen “by osmosis”?
    A. The propagation of an action potential along an axon
    B. Sodium leaving a cell and potassium entering the cell
    C. Learning the names of skeletal muscles
    D. Water passing through a membrane

Answer 29

Answer is D: Osmosis is a word used to describe the movement of water through a membrane from the side where the concentration of water molecules is greater to the side where the water concentration is lower.

Question 30

29. Given that deoxygenated blood in the pulmonary capillaries has an oxygen concentration of 40 mmHg and carbon dioxide concentration of 46 mmHg and alveolar air has an oxygen concentration of 104 mmHg and carbon dioxide concentration of 40 mmHg, in which directions will oxygen and carbon dioxide diffuse?
    A. Oxygen will diffuse from capillary blood to alveolar air; carbon dioxide will diffuse from the blood into the alveoli.
    B. Oxygen will diffuse from alveolar air to capillary blood; carbon dioxide will diffuse from the alveoli into the blood.
    C. Oxygen will diffuse from alveolar air to capillary blood; carbon dioxide will diffuse from blood to the alveoli.
    D. Oxygen will diffuse from capillary blood to alveolar air; carbon dioxide will diffuse from blood to the alveoli.

Answer 30

Answer is C: Of course O2 diffuses from alveoli to blood, while CO2 diffuses from blood to alveoli. Or by considering movement down the concentration gradients: O2 from 104 to 40 mmHg and CO2 from 46 to 40 mmHg.

Question 31

30. Only one of the definitions of osmotic pressure below is correct. Which one?
    A. The hydrostatic pressure required to halt osmosis is called osmotic pressure.
    B. Water pressure that develops in a solution as a result of osmosis into that solution is called osmotic pressure.
    C. Osmotic pressure is the pressure exerted by the movement of water across a semipermeable membrane due to the difference in solution concentration.
    D. Osmotic pressure is the force required to prevent water from moving by osmosis across a selectively permeable membrane.

Answer 31

Answer is A: The other three choices, despite all being quotations from anatomy and physiology textbooks, are wrong. Osmotic pressure is not a force; water movement does not exert a pressure; osmosis between compartments in the body does not cause water pressure to develop.

Question 32

1. What information does the molarity of a solution provide?
   A. The density of a solution
   B. The number of dissolved particles per litre of solution C. The mass of a mole of the substance
   D. The tonicity of the solution

Answer 32

Answer is B: If molarity is 1.2 mmol/L = 1.2 × 10−3 × (6.02 × 10^23) particles per litre.

Question 33

2. What term is applied to an intravenous solution that would cause a net movement
   of water out of red blood cells?
   A. Hypertonic
   B. Supertonic
   C. Hypotonic
   D. Isotonic

Answer 33

Answer is A: “Hyper-” refers to greater (tonicity) than inside a RBC. Hence water would move from the less concentrated solution (within the RBC) to the exterior.

Question 34

3. What is a definition of an osmole? The amount of substance that:
   A. Must be dissolved to produce 6 × 1023 solute particles
   B. Must be dissolved to produce an osmotic pressure of 1.0 mmHg
   C. Must be dissolved to produce an isotonic solution
   D. Contains6×1023 particles

Answer 34

Answer is A: Ionic substances (e.g. Na+Cl−) separate into ions when dissolved. Hence a mole of NaCl would produce two osmoles of ions (1 mol of Na ions and 1 mol of Cl ions). Hence half of a mole of NaCl, when dissolved, would result in one osmole of dissolved particles (ions).

Question 35

4. Choose the solution below that has the lowest concentration of dissolved particles.
   A. 0.9% NaCl
   B. Isotonic powerade
   C. 5% glucose
   D. Hypotonic saline

Answer 35

Answer is D: Choices A, B and C are all isotonic solutions. “Hypo-” refers to a solution concentration that is less than that of human blood.

Question 36

5. What can be correctly said of an isotonic intravenous solution? An isotonic solution:
   A. Causes water to move out of red blood cells
   B. Causes no net movement of water into or out of red blood cells
   C. Has the same solutes in the same solution concentration as blood plasma
   D. Causes water to move into red blood cells

Answer 36

Answer is B: Isotonic means that the IV solution has the same concentration of particles (albeit the particles themselves may be different) as in RBC; hence there is no net osmotic flow.

Question 37

6. What would be the concentration of a solution that causes red blood cells placed in it to swell?
   A. Hypotonic
   B. Isotonic
   C. Hypertonic
   D. Iso-osmotic

Answer 37

Answer is A: If the RBC swell, that means water is entering the cells; hence the surrounding liquid is at a lower concentration (i.e. hypotonic) to the liquid inside RBC.

Question 38

7. The unit milliosmoles per litre (mosmol/L) refers to which of the following?
   A. The number of particles in solution, in multiples of 6 × 1020 per litre
   B. 103 times the number of moles of particles in a litre of solution
   C. The number of molecules per litre of solution
   D. The number of moles per millilitre of solution

Answer 38

Answer is A: A milliosmole (mosmol) is 10−3 × (6 × 1023) particles which is 6 × 1020. Choice B means 1000× the correct answer. Choice D means 1/1000× the correct answer.

Question 39

8. A hypertonic solution is one which:
   A. Has an osmotic pressure that is different to that inside red blood cells
   B. Has an osmolarity less than that of red blood cells
   C. Causes no net movement of water through the membrane of red blood cells
   D. Has an osmolarity greater than that of red blood cells

Answer 39

Answer is D: “Hyper-” means greater than the tonicity (or osmolarity) inside a RBC.

Question 40

9. Given that 1 mol of Na+Cl− has a mass of 58.5 g, what would be the concentration of particles when 0.9 g of Na+Cl− is dissolved in 100 ml of water?
   A. 117 mmol/L
   B. 150 mmol/L
   C. 150 mosmol/L
   D. 300 mosmol/L

Answer 40

Answer is D: The number of moles in 0.9 g = 0.9 g/58.5 g/mol = 0.0154 mol of Na+Cl−. However NaCl separates into ions when dissolved, so that there will be 0.0154 mol of Na and 0.0154 mol of Cl; hence 0.0308 osmol of particles = 30.8 mosmol per 100 ml. In 1 L, the number of moles would be ten times greater, so 300 mosmol/L (is closest).

Question 41

10. The unit millimoles per litre (mmol/L) refers to which of the following?
    A. The number of particles in solution, in multiples of 6 × 1020 per litre B. 103 times the number of moles of particles in a litre of solution
    C. The number of molecules per litre of solution
    D. The number of moles per millilitre of solution

Answer 41

Answer is A: A mole = 6 × 1023 particles, a millimole (mmol) = 6 × 1020 particles. When dissolved, whether the particles are ions or molecules makes no difference.

Question 42

11. An isotonic solution is one which:
    A. Has an osmotic pressure that is different to red blood cells
    B. Has an osmolarity less than that of red blood cells
    C. Causes no net movement of water between the solution and red blood cells
    D. Has an osmolarity greater than that of red blood cells

Answer 42

Answer is C: “Iso-” means “the same”. When the concentration of the surrounding liquid is the same as that inside a RBC, then no net water movement occurs.

Question 43

12. A hypotonic solution may be characterised by which of the following?
    A. A solution whose osmolarity is greater than that of blood B. One that causes red blood cells to crenate
    C. A solution within the range 280–300 mosmol/L
    D. One that causes a net water movement into red blood cells

Answer 43

Answer is D: “Hypo-” means less concentrated than the solution inside a RBC. This in turn means that the concentration of water molecules is greater outside the cell than inside. So there will be a net water flow by osmosis into the RBC.

Question 44

13. Which of the following statements could be applied to a hypertonic solution?
    A. It causes red blood cells to shrink and crenate.
    B. It causes red blood cells to swell and perhaps lyse.
    C. It is a solution with an osmolarity less than that of blood.
    D. It causes movement of water into red blood cells.

Answer 44

Answer is A: RBC placed in a hypertonic solution would lose water to the solution, so their volume would decrease (they would shrink). This would cause their membrane to become wrinkled (to crenate).

Question 45

14. To what does the term “mole” refer?
    A. The smallest particle of a molecular compound
    B. The amount of solute that must be dissolved in water to make an isotonic
    solution
    C. An amount of substance that contains 6.02 × 1023 particles
    D. A group of two or more atoms bonded together

Answer 45

Answer is C: Mole is the SI unit for “amount of substance”. Choice C is the correct number.

Question 46

15. What do solutions of 5% glucose, 9.5% sucrose and 0.9% sodium chloride have in common? They:
    A. All have the same concentration
    B. Are all hypotonic to plasma
    C. All contain the same number of dissolved particles per unit volume D. Are all hypertonic to plasma

Answer 46

Answer is C: The three solutions are isotonic to blood. Choice A is incorrect; they have different (weight/volume) concentrations.

Question 47

16. An intravenous fluid that is hypertonic to blood would have what effect on the red blood cells?
    A. It would have no effect.
    B. The number of red blood cells would increase.
    C. Red blood cells would lyse.
    D. It would cause red blood cells to crenate.

Answer 47

Answer is D: RBC in contact with a hypertonic solution would lose water to the solution and shrink. This would cause their plasma membrane to crenate (wrinkle).

Question 48

17. An intravenous fluid that is isotonic to blood would have what effect on the red blood cells?
    A. It would have no effect.
    B. It would cause red blood cells to crenate.
    C. Red blood cells would lyse.
    D. The blood volume would increase.

Answer 48

Answer is A: RBC would be unaffected by an isotonic solution as there will be no net flow of water into or out of the cells.

Question 49

18. What may be said of isotonic solutions? They have:
    A. Had added the same number of moles of solid substance per volume of solution
    B. The same number of grams of solute per volume of solution
    C. The same percent concentration
    D. The same number of dissolved particles per volume of solution

Answer 49

Answer is D: Choice A is incorrect as a mole of an ionic substance will result in 2 or 3 osmoles of dissolved particles. (Choices B and C are incorrect.)

Question 50

19. Fructose is a sugar with a molecular formula C6H12O6. Given that the atomic weights are C = 12, H = 1 and O = 16, how many moles of fructose are there in 36 g?
    A. 0.01 mol
    B. 0.10 mol
    C. 0.20 mol
    D. 0.50 mol

Answer 50

Answer is C: Mass of 1 mol of fructose = (6×12) + (12×1) + (6×16) = 72+12+96 = 180 g. 36 g is less than 1 mol. Number of moles = 36 g/180 g per mol = 0.2 mol.

Question 51

20. Ribose is a sugar with molecular formula C5H10O5. Given that the atomic weights are C = 12, H = 1 and O = 16, how many moles of ribose are there in 3 g?
    A. 0.01 mol
    B. 0.02 mol
    C. 0.05 mol
    D. 0.10 mol

Answer 51

Answer is B: Mass of 1 mol of ribose = (5 × 12) + (10 × 1) + (5 × 16) = 60 + 10 + 80 = 150 g. 3 g is less than 1 mol. Number of moles = 3 g/150 g per mol = 0.02 mol.

Question 52

21. A solution is prepared containing 2% sodium chloride (Na+Cl−). Which of the following best describes the osmolarity of this solution? (Note: Na = 23, Cl = 35.5)
    A. 340 mosmol/L
    B. 680 mosmol/L
    C. 340 osmol/L
    D. 680 osmol/L

Answer 52

Answer is B: 2% = 2 g/100 ml = 20 g/L. Mass of 1 mol of Na+Cl−
= 23 + 35.5 = 58.5 g. Number of moles of Na+Cl− required for 1 L of 2% solution = 20 g/58.5 g per mol = 0.34 mol. Sodium chloride is an ionic substance so dissociates into ions when dis- solved. This would produce 0.34 mol of Na and 0.34 mol of Cl = 0.68 osmoles of
dissolved particles in the 1 L. 0.68 osmol/L = 680 mosmol/L

Question 53

22. The isotonic concentration for sodium chloride is 0.9% and for glucose is 5%. Which of the following solutions is isotonic with the above solutions? A solution containing:
    A. 5% glucose and 0.25% sodium chloride
    B. 0.9% sodium chloride and 0.5% glucose
    C. 2.5% sodium chloride and 2.5% glucose
    D. 4% glucose and 0.18% sodium chloride

Answer 53

Answer is D: Choices A and B are both hypertonic. Four percent glucose contains 4/5 of the concentration of dissolved particles that are in (isotonic) 5% glucose. 0.18% sodium chloride contains 1/5 of the concentration of dissolved particles that are in 0.9% sodium chloride (0.18/0.9 = 0.2). One fifth plus four fifths add to five fifths of the number of particles that are required for an isotonic solution.

Question 54

23. Given that 1 mol of glucose has a mass of 180 g, how many millimole of glucose does 40 g of glucose contain?
    A. 0.222
    B. 180
    C. 222
    D. 278

Answer 54

Answer is C: Number of moles of glucose = 40/180 = 0.222 mol. Number of milli- moles = 222.

Question 55

24. Which of the following statements about an “osmole” is correct? An osmole is the:
    A. Same as a mole for ionic substances
    B. Formula weight of a substance expressed in grams
    C. Number of moles multiplied by the number of molecules in the chemical formula
    D. Amount of substance that must be dissolved in order to produce 1.6 × 1023 dissolved particles

Answer 55

Answer is D: An osmole refers to the number of solute particles (ions or molecules) that exist in solution, after a substance has dissolved.

Question 56

25. Glucose is a sugar with a molecular formula C6H12O6. Given that the atomic weights are C = 12, H = 1 and O = 16, what is the mass of 1 mol of glucose?
    A. 1.8 g
    B. 18 g
    C. 180 g
    D. 1800 g

Answer 56

Answer is C: Mass of 1 mol of glucose = (6×12)+(12×1)+(6×16) = 72+12+96 = 180 g.

Question 57

26. Lactose is a sugar with a molecular formula C12H22O11. Given that the atomic weights are C = 12, H = 1 and O = 16, what is the weight of 1 mol of lactose?
    A. 3.42 g
    B. 34.2 g
    C. 342 g
    D. 3420 g

Answer 57

Answer is C: Mass of 1 mol of lactose = (12×12)+(22×1)+(11×16) = 144+22+176 = 342 g.

Question 58

27. Red blood cells are added to a hypotonic solution of glucose. Which of the following best describes what you would observe?
    A. The cells would most likely sink to the bottom unaffected.
    B. The cells would shrink due to water loss.
    C. The cells would coagulate.
    D. The cells would swell and burst due to intake of water.

Answer 58

Answer is D: A hypotonic solution would result in an inflow of water to RBC. This would stretch their plasma membrane, and eventually it would break (burst).

Question 59

28. A solution that is said to be isotonic to blood has the same:
    A. Percent concentration as blood
    B. Number of moles of dissolved particles as blood
    C. Number of osmoles per litre of dissolved particles as blood
    D. Number of dissolved particles as blood

Answer 59

Answer is C: Isotonic means the same number of solute particles per litre. Choice B would also be correct if “moles” was replaced with “moles per litre”.

Question 60

29. If the following amounts of the given substances were dissolved in water, which would result in four osmoles of dissolved particles?
    A. 2 mol of C6H12O6
    B. 2 mol of Na+Cl−
    C. 2 mol of C12H22O11 D. 2 mol of (Na+)2SO42−

Answer 60

Answer is B: Osmole is a term used when the solute particles came from an ionic substance. Osmoles = moles × number of ions in formula. There are two ions in the formula for sodium chloride, hence 4 osmoles. There are three ions in the formula for sodium sulphate, hence 6 osmoles.

Question 61

30. What is the difference between “molarity” and “osmolarity”?
    A. Molarity applies only to covalent compounds, while osmolarity applies only to ionic compounds.
    B. Osmolarity is molarity multiplied by two.
    C. The molarity and osmolarity of a solution are the same for dissolved ionic
    compounds but are different for dissolved covalent compounds.
    D. Osmolarity refers to the concentration of dissolved particles in a solution which may not be the same as the number of moles of substance that was
    dissolved per litre of solution.

Answer 61

Answer is D: Choice D is better than choice A as molarity can also be applied to ionic compounds.

Question 62

31. Human blood has an osmolarity that lies within the range 280– 300 mosmol/L. Which of the following statements is correct?
    A. An isotonic solution has osmolarity that is either less than 280 or greater than 300 mosmol/L.
    B. A hypotonic solution has osmolarity between 280 and 300 mosmol/L.
    C. A hypertonic solution has osmolarity between 280 and 300 mosmol/L.
    D. An isotonic solution has osmolarity between 280 and 300 mosmol/L.

Answer 62

Answer is D: An isotonic solution has the same osmolarity as blood.

Question 63

32. What distinguishes an osmole from a mole?
    A. In a sample of substance, the number of osmoles is twice the number of moles.
    B. Both mole and osmole may be used in reference to ionic compounds, while covalent compounds are described by mole alone.
    C. The mass of a mole is the sum of the relative atomic masses (RAM) of the atoms in the formula stated as grams. An osmole is half of this mass.
    D. An osmole applies only to covalent molecular substances, whereas a mole is validly applied to both covalent and ionic substances.

Answer 63

Answer is B: Both mole and osmole may be used in reference to ionic compounds (because the atoms of ionic compounds separate into their constituent ions when dissolved), while the atoms within covalent compounds remain as molecules even when dissolved.

Question 64

33. Which of the four IV solutions below is hypotonic?
    A. 0.18% sodium chloride and 4% glucose
    B. 0.3% sodium chloride and 3.3% glucose
    C. 0.45% sodium chloride
    D. 0.9% sodium chloride

Answer 64

Answer is C: As 0.9% NaCl is isotonic, and 0.45% is less than 0.9%, it must be hypotonic (and there is only one best correct answer!). A is “4% and a fifth” while B is “3.3% and a third”.

Question 65

34. Which of the following solutions is the most hypertonic?
    A. 0.3% sodium chloride and 3.3% glucose
    B. 0.45% sodium chloride and 2.5% glucose
    C. 0.45% sodium chloride
    D. 10% glucose

Answer 65

Answer is D: 5% glucose is isotonic, so 10% must be hypertonic. Choices A and B are isotonic, while choice C is hypotonic.

Question 66

35. Given that a mole is 6 × 1023 particles, what is a millimole?
    A. 6×1020 particles
    B. 1000 mol
    C. 6×1026 particles
    D. 0.0001 mol

Answer 66

Answer is A: A millimole is one thousandth (or 0.001) of a mole.1 mmol = 10−3×(6×1023)=6×1020 particles

Question 67

36. A solution that is isotonic to blood plasma is one which:
    A. Contains 0.5% glucose
    B. Must contain the same solutes as blood and in the same concentration as in
    blood
    C. Has an osmolarity between 280 and 300 mosmol/L
    D. Causes no net movement of water into or out of cells

Answer 67

Answer is D: The concept of tonicity involves reference to a membrane (in this case the plasma membrane of a RBC). Osmolarity is a property of the solution (and of how much solute is dissolved in it) and exists whether a semipermeable membrane is present or not.

Question 68

37. Which of the following quantities of substance would, when dissolved in 1 L of water, produce a solution with the highest osmolarity?
    A. 1 mol of glucose molecules (C6H12O6)
    B. 1 mol of Na+Cl− (sodium chloride)
    C. 1 mol of haemoglobin molecules
    D. 1 osmole of K+ (potassium ions)

Answer 68

Answer is B: Sodium chloride is an ionic substance, so when it dissolves, 1 mol of it would separate into 1 mol of individual Na+ ions and 1 mol of Cl− ions giving a total of 2 osmoles of separate particles (ions) per litre.

Question 69

38. Given the concentration of Na+ inside the cell, it is about 10 mmol/L, while it is 140 mmol/L in the extracellular fluid. The values for K+ are 140 mmol/L inside the cell and 4 mmol/L extracellularly. In what directions would these ions diffuse?
    A. Na+ would diffuse into the cell while K+ would diffuse out.
    B. K+ would diffuse into the cell while Na+ would diffuse out.
    C. Both Na+ and K+ would diffuse out of the cell.
    D. Both Na+ and K+ would diffuse into of the cell.

Answer 69

Answer is A: Na would diffuse form 140 mmol/L to 10 – the direction of its concentration gradient which is from outside to inside. K would diffuse from 140 mmol/L to 4, that is, from inside to outside.

Question 70

39. Which of the following statements best describes what all isotonic solutions have in common? They:
    A. Contain the same concentration of glucose molecules
    B. Contain the same total concentration of particles
    C. Contain the same concentration of sodium chloride
    D. Have the same specific gravity

Answer 70

Answer is B: While “iso-” refers to the same, it is the concentration of all the dissolved particles be they ions or molecules of any substance that determines tonicity.

Question 71

40. Which statement is INCORRECT? Colloid osmotic pressure:
    A. Is the difference in solution concentration between plasma and interstitial fluid
    B. Refers to the greater solution concentration of plasma, compared to interstitial fluid, due to the plasma proteins
    C. Causes water to be drawn into blood from the interstitial fluid
    D. Is the pressure exerted on capillary walls due to the collision of the plasma proteins

Answer 71

Answer is D: Although colloid osmotic pressure has the word “pressure”, this does not mean that a physical pressure is exerted on capillary walls due to the colloids (the plasma proteins).

Question 72

41. Consider a volume of 100 ml of each of the four solutions below. Which would contain the greatest number of osmoles of dissolved particles? (FYI the atomic masses of H = 1, C = 12, O = 16, Na = 23, Cl = 35.5)
    A. 5% ethanol: C2H6O
    B. 5% glucose: C6H12O6
    C. 5% sodium chloride: Na+ Cl−
    D. 10% glucose: C6H12O6

Answer 72

Answer is C: By adding the masses of the atoms in the formula, we can determine that 1 mol of each substance has a mass of 46 g (for ethanol: 2 × 12 + 6 × 1 + 1 × 16 = 46), 180 g (glucose) and 58.5 g (NaCl). “5%” means 5 g of substance (much less than 1 mol of each substance) is dissolved in 100 ml of solution. An ethanol molecule is much less than half the mass of a glucose molecule, so there are more than twice as many ethanol molecules as glucose molecules in a 5% solution. Hence the ethanol solution has more osmoles than either glucose solution. While NaCl has a greater formula mass than ethanol, NaCl is an ionic substance, so it separates into Na ions and Cl ions when dissolved. This doubling in the number of particles when NaCl dissolves means that choice C contains the greatest number of osmoles. Or by cal- culation, the number of osmoles in each 100 ml of solution is determined by divid- ing the mass of dissolved substance by the mass of 1 mol of that substance for 5% ethanol, 5/46 = 0.109; 5% glucose, 5/180 = 0.0278; NaCl, (5/58.5) × 2 = 0.171; and 10% glucose, 10/180 = 0.0556 osmoles per 100 ml.

Question 73

42. A healthy concentration of sodium in the blood is typically 140 mmol/L. How many grams of sodium are there in a litre of blood? (atomic mass of Na = 23)
    A. 23 ÷ 140 = 0.164 g
    B. 23 ÷ 0.14 = 164.3 g
    C. 23×140 = 3220 g
    D. 23×0.14 = 3.22 g

Answer 73

Answer is D: The number of moles of a substance is determined by dividing the mass of substance by the mass of 1 mol of substance. One mole of sodium has a mass of 23 g: 140 mmol/L = 0.140 mol/L = mass of Na dissolved in 1 L (in gram) ÷ 23. Hence mass of Na = 23×0.14 = 3.22 g/L

Question 74

43. A healthy concentration of chloride in the blood is typically 105 mmol/L. How many grams of chloride are there in a litre of blood? (atomic mass of Cl = 35.5)
    A. 35.5×105 = 3727 g
    B. 35.5 × 0.105 = 3.73 g
    C. 35.5 ÷ 0.105 = 338.1 g
    D. 35.5 ÷ 105 = 0.3381 g

Answer 74

Answer is B: The number of moles of a substance in a solution is determined by dividing the mass of dissolved substance by the mass of 1 mol of the substance. One mole of chloride has a mass of 35.5 g: 105 mmol/L = 0.105 mol/L. So 0.105 mol/L = mass of Cl (in gram) ÷ 35.5. Rearrange this formula, hence mass of Cl = 35.5×0.105 = 3.73 g/L

Question 75

44. A blood concentration of glucose that is indicative of diabetes is 12 mmol/L. What % concentration of glucose is this equivalent to? (The formula for glucose is C6H12O6; atomic mass of C = 12, H = 1, O = 16; mass of a mole = sum of masses of atoms in formula.)
    A. 0.012%
    B. 0.216%
    C. 5%
    D. 12%

Answer 75

Answer is B: (By calculation) Percent concentration refers to how many grams are dissolved in 100 ml of solution.One mole of glucose has a mass of 180 g. (6 × 12) + (12 × 1) + (6 × 16) = 180.12 mmol/L = 0.012 mol/Lmol/L = (mass/L)÷(mass of 1 mol): hence 0.012 mol/L = (mass/L)÷180; so mass = 180×0.012 = 2.16 g/ L2.16 g/L = 0.216 g/100 ml = 0.216%(Alternatively: The answer can’t be 5% as this is an isotonic glucose solution. Hence neither is it 12% as this is hypertonic. % conc is not the same number as mol/L, so the answer is not A.)

Question 76

45. If 1 mol of magnesium chloride (Mg2+ Cl− ) was dissolved in a litre of water, 2
    how many osmoles would be present in the solution?
    A. 1 osmole
    B. 2 osmoles
    C. 3 osmoles
    D. 4 osmoles

Answer 76

Answer is C: From the given formula, there are three ions in the solution, one magnesium and two chloride, which would disassociate in solution. This would produce three osmoles of ions.

Question 77

46. A bag containing 1 L of prepared intravenous saline solution is printed with “isotonic approximate osmolality 300 mOsm”. What is meant by osmolality?
    A. It is the number of osmoles dissolved in kilogram of water.
    B. It is the number of osmoles dissolved per litre of saline solution.
    C. Osmolality is an alternate spelling for osmolarity, the number of osmole per
    litre of solution.
    D. Osmolality is used for covalent solutes, while osmolarity is used for ionic
    solutes.

Answer 77

Answer is A: As osmolality (osmol/kg) refers to the concentration within a mass (a kilogram) of solution it is unaffected by the temperature of the solution. Osmolarity (with an “r”) in osmol/L refers to the concentration within a volume of a litre of solution. For human physiological solutions which are relatively dilute, there is virtually no difference between the concentrations of solutions when expressed as osmolarity or osmolality.

Question 78

47. Given that urea has the formula H2NCONH2 and the atomic weights H = 1, C = 12, N = 14 and O = 16, what is the mass of 1 mol of urea?
    A. 71 g
    B. 60 g
    C. 45 g
    D. 43 g

Answer 78

Answer is B: Multiply the number of atoms of each element (H, C, N, O) in the formula by the element’s atomic weight to get mass of a mole. Hence: (4 × 1) + (1 × 12)+(2×14)+(1×16) = 4+12+28+16 = 60 g.

Question 79

48. A human excretes approximately 450 mmol of urea in urine each day. Given the molar mass of urea is 60 g, what is the mass of urea excreted daily?
    A. 27 g
    B. 60 g
    C. 270 g
    D. 450 g

Answer 79

Answer is A: As the molar mass of urea is 60 g, this means that 1 mol of urea has a mass of 60 g. Now 450 mmol is LESS than 1 mol, so the number must be less than 60 g.
By numbers: 450 mmol × 60 g/mol = 0.45×60 = 27 g