$$\text{Osmolarity} = 0.154\ \text{mol/L} \times 2 = 0.308\ \text{osmol/L}$$

$$\text{Molarity} = \frac{0.90\ \text{g}}{58.44\ \text{g/mol} \times 0.100\ \text{L}} = 0.154\ \text{mol/L}$$

$$\text{Osmolarity} = \text{Molarity} \times \text{number of particles per formula unit}$$

Question 1

Which of the following best explains why a 0.90% (m/v) NaCl solution is considered isotonic to human blood?

Accepted Answer

Because its osmolarity is equal to that of blood plasma, preventing net movement of water across red blood cell membranes.

Question 2

Calculate the osmolarity of a 0.90% (m/v) NaCl solution. (Molar mass of NaCl = 58.44 g/mol).

Accepted Answer

$$	ext{Osmolarity} = 0.154\ 	ext{mol/L} 	imes 2 = 0.308\ 	ext{osmol/L}$$

Question 3

A patient accidentally receives a hypotonic IV solution. What is the most likely effect on their red blood cells?

Accepted Answer

Water will enter the cells, causing them to swell and possibly burst (hemolysis).

Question 4

If a patient receives a hypertonic NaCl solution, what will happen to their red blood cells?

Accepted Answer

Water will leave the cells, causing them to shrink (crenation).

Question 5

Which calculation correctly determines the molarity of NaCl in a 0.90% (m/v) solution?

Accepted Answer

$$	ext{Molarity} = \frac{0.90\ 	ext{g}}{58.44\ 	ext{g/mol} 	imes 0.100\ 	ext{L}} = 0.154\ 	ext{mol/L}$$

Question 6

Which of the following best describes an isotonic solution?

Accepted Answer

A solution with the same osmotic pressure as the cells, resulting in no net movement of water.

Question 7

A nurse must prepare an IV solution that is isotonic to blood. Which concentration of NaCl should she use?

Accepted Answer

0.90% (m/v)

Question 8

Which of the following statements about osmolarity is correct?

Accepted Answer

Osmolarity is the total concentration of all solute particles in a solution, measured in osmol/L.

Question 9

A 0.45% (m/v) NaCl solution is administered to a patient. Compared to blood, this solution is:

Accepted Answer

Hypotonic, and may cause red blood cells to swell.

Question 10

Which equation would you use to calculate the osmolarity of a NaCl solution?

Accepted Answer

$$	ext{Osmolarity} = 	ext{Molarity} 	imes 	ext{number of particles per formula unit}$$

Question 11

A patient receives an IV solution that is hypertonic to their blood. What is the most likely outcome?

Accepted Answer

Their red blood cells will lose water and shrink.

Question 12

Which of the following best describes the effect of an isotonic NaCl solution on red blood cells?

Accepted Answer

There is no net movement of water, and the cells retain their normal shape.

Osmolarity and Tonicity of NaCl Solutions in Human Blood

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