Gas solubility

Question 1

With regard to the solubility of gases: Henry’s Law describes the relationship between the amount of gas dissolved in a liquid and the partial pressure of the gas in equilibrium with the liquid

Answer 1

True. Henry’s Law states that gas the amount of gas dissolved in a solution is proportional to the partial pressure of the gas, at a constant temperature.

Question 2

With regard to the solubility of gases: At a constant pressure, the amount of gas that dissolves in a liquid increases as the temperature of the liquid increases

Answer 2

False. Gas solubility decreases with increasing temperature.

Question 3

With regard to the solubility of gases: The Ostwald solubility coefficient describes the volume of gas dissolved in a liquid and is dependent on pressure

Answer 3

False. The Ostwald solubility coefficient is of more practical use in anaesthesia because it is independent of pressure, provided the volume of dissolved gas is measured at the ambient pressure.

Question 4

With regard to the solubility of gases: The Bunsen solubility coefficient is commonly used in anaesthetic practice as it is independent of pressure

Answer 4

False. The Bunsen solubility coefficient is not used in anaesthesia. It is dependent on pressure.

Question 5

With regard to the solubility of gases: The solubility of gases in liquids depends both on the type of gas and the type of liquid involved

Answer 5

True. Gas solubility changes with both the type of gas and the type of liquid concerned.

Question 6

With regard to gas solubility: A rapid onset of action of an inhalational anaesthetic agent is associated with a high blood:gas solubility coefficient

Answer 6

False. Rapid onset is associated with a poorly blood-soluble agent and therefore a low blood:gas coefficient.

Question 7

With regard to gas solubility: Nitrous oxide has a lower blood:gas solubility coefficient than halothane

Answer 7

True. Nitrous oxide has low blood:gas coefficient (0.47) and therefore a rapid onset of action. Halothane has a high coefficient (2.4).

Question 8

With regard to gas solubility: The Meyer-Overton theory relates the oil:gas solubility coefficients of inhalational anaesthetic agents to potency

Answer 8

True. The Meyer-Overton theory describes the positive association between oil:gas solubility and potency.

Question 9

With regard to gas solubility: Isoflurane has a higher oil:gas solubility coefficient than sevoflurane

Answer 9

True. Soflurane has a higher oil:gas solubility coefficient (98) than sevoflurane (80) and is more potent (and has a lower MAC).

Question 10

With regard to gas solubility: Inhalational anaesthetic agents are more soluble in oil than in blood

Answer 10

True. All inhalational anaesthetic agents are more soluble in oil than blood.

Question 11

The amount of gas dissolved in a liquid at constant ambient pressure at equilibrium depends on: Temperature of the liquid

Answer 11

True. The solubility of a gas decreases with increasing temperature.

Question 12

The amount of gas dissolved in a liquid at constant ambient pressure at equilibrium depends on: Partial pressure of the gas

Answer 12

True. Henry’s Law states that the amount of dissolved gas is directly proportional to the partial pressure of the gas in equilibrium with it, at a constant temperature.

Question 13

The amount of gas dissolved in a liquid at constant ambient pressure at equilibrium depends on: The diffusion coefficient

Answer 13

False. The diffusion coefficient is not related to gas solubility.

Question 14

The amount of gas dissolved in a liquid at constant ambient pressure at equilibrium depends on: Solubility of the gas in the liquid

Answer 14

True. The solubility of gases depends both on the type of gas and the type of liquid.

Question 15

The amount of gas dissolved in a liquid at constant ambient pressure at equilibrium depends on: Critical temperature of the gas

Answer 15

False. The critical temperature is the temperature above which a gas cannot be liquified irrespective of the pressure applied. It has no influence on gas solubility.

Question 16

With regard to the solubility of gases in solution: The Bunsen coefficient must be corrected to STP

Answer 16

True. The Bunsen coefficient is not used in anaesthetic practice but requires correction to STP.

Question 17

With regard to the solubility of gases in solution: When using the partition coefficient, one of the phases must be a gas

Answer 17

False. The partition coefficient is a ratio and can be used to describe relative solubilities of two liquids.

Question 18

With regard to the solubility of gases in solution: The order of the phases need not be specified with the partition coefficient

Answer 18

False. For partition coefficients, reversing the order of the phases gives the reciprocal ratio value.

Question 19

With regard to the solubility of gases in solution: Henry’s law is independent of temperature

Answer 19

False. Henry’s Law states that the amount of dissolved gas is directly proportional to the partial pressure of the gas in equilibrium with it. The temperature must remain constant because this affects gas solubility.

Question 20

With regard to the solubility of gases in solution: Henry’s law is independent of temperature

Answer 20

True. Henry’s Law is defined above and applies to any liquid, provided the gas and liquid type remain constant

Question 21

With regard to the solubility of gases Osmolality is the number of osmotically active particles per litre of solvent

Answer 21

False. Osmolality is the number of osmotically active particles per kilogram of solvent.

Question 22

With regard to the solubility of gases Tonicity is the osmolality due to effective osmoles in a solution

Answer 22

True. Tonicity refers to the effective osmoles

Question 23

With regard to the solubility of gases Osmolarity in the blood may be estimated by the formula: (Na+ + K+) + glucose + urea

Answer 23

False. Osmolarity can be estimated by the formula: 2 x (Na+ + K+) + urea + glucose.

Question 24

With regard to the solubility of gases Osmolarity is measured in milliosmoles per kilogram of water

Answer 24

False. Osmolarity is measured in miliosmoles per litre of water.

Question 25

With regard to the solubility of gases One mole of large solute molecules exerts the same osmotic pressure compared with one mole of small solute molecules across a semi-permeable membrane

Answer 25

True. The size of the molecules does not affect osmotic pressure, it is the number of particles.

Question 26

Isotonic means the same as isosmolar

Answer 26

False. Molarity refers to the number of osmoles in solution whereas tonicity refers to the effective osmoles in solution.

Question 27

Increasing solute load causes depression of the solvent vapour pressure

Answer 27

True. This is one of the four colligative properties.

Question 28

Colligative properties include freezing point elevation and boiling point depression

Answer 28

False. Colligative properties include freezing point depression and boiling point elevation.

Question 29

Colligative properties are employed in an osmometer

Answer 29

True. Osmometers employ colligative properties to measure osmolality.

Question 30

Two moles of glucose give as many osmoles as two moles of sodium chloride (NaCl)

Answer 30

False. Two moles of sodium chloride will give 4 osmoles when in solution because the ions separate out when in solution.

Question 31

Colligative properties are properties that are influenced by the nature of the solute and the number of osmotically-charged particles

Answer 31

False. Colligative properties are not influenced by the nature of the solute in a solution.

Question 32

With increasing numbers of particles in a solution, the solvent vapour pressure above the solution will increase

Answer 32

False. Increasing solute load leads to a reduction in the solvent vapour pressure.

Question 33

Adding one mole of a substance to one kilogram of water increases the freezing point by 1.86°C

Answer 33

False. One mole of a substance added to one kilogram of water depresses the freezing point by 1.86oC.

Question 34

Raoult’s Law states that depression of the vapour pressure of a solvent is proportional to the molar concentration of the solute

Answer 34

True. This is Raoult’s Law. Some osmometers employ this to measure osmolality

Question 35

Dissolved molecules alter the physical properties of solutions

Answer 35

True. The colligative properties are evidence of this.