, PLEASE USE THIS DOCUMENT AS A GUIDE TO ANSWER YOUR ASSIGNMENT
Question 1
1. Various factors influence the amount of gas that can dissolve in water. Name and briefly
describe the direction of influence of the four main such factors discussed in the learning
material.
The four main factors are:
The type of gas (page 10-11) - Different gases have different solubilities. CO₂ is much more
soluble than O₂.
The pressure of the gas (page 11) - According to Henry's law, more gas dissolves at higher
pressure.
The temperature (page 11-12) - The colder the temperature, the more gas is dissolved.
The presence of other solutes (page 12-13) - More substances dissolved in water (like in
seawater) reduces gas solubility compared to freshwater.
Factors Influencing Gas Solubility in Water
The solubility of gases in water is determined by four main physical factors that dictate the difficulty
or ease with which organisms can extract oxygen from their aquatic environment (ZOL2601, Study
Guide. p. 10).
Type of Gas
The chemical nature of the gas itself fundamentally determines its solubility, as different gases
exhibit vastly different solubility coefficients. Carbon dioxide, for instance, is substantially more
soluble in water than oxygen due to its chemical properties and its ability to react with water to form
carbonic acid and subsequent bicarbonate ions (ZOL2601, Study Guide. pp. 10-11, 12).
Pressure of the Gas
The partial pressure of the gas in the gas phase directly influences dissolution, as described by
Henry's law. When the pressure of a gas above water increases, the quantity of that gas dissolving
into the water increases proportionally; conversely, reducing pressure causes gases to leave solution
(ZOL2601, Study Guide. pp. 11, 13).
Temperature
Temperature exerts a strong inverse relationship on gas solubility, wherein colder temperatures
permit greater quantities of gas to remain dissolved in water. As temperature rises, the kinetic energy
of water molecules increases, reducing the capacity of water to retain dissolved gases, which
explains why polar oceans contain more dissolved oxygen than tropical waters (ZOL2601, Study
Guide. pp. 11-12).
Presence of Other Solutes
The concentration of other dissolved substances in water decreases the solubility of gases through
competitive interactions for solvent capacity. Seawater, containing numerous dissolved salts,
demonstrates lower oxygen solubility than freshwater at equivalent temperatures and pressures, as
the dissolved ions effectively reduce the water's capacity to accommodate additional gas molecules
(ZOL2601, Study Guide. pp. 12-13).
Question 1
1. Various factors influence the amount of gas that can dissolve in water. Name and briefly
describe the direction of influence of the four main such factors discussed in the learning
material.
The four main factors are:
The type of gas (page 10-11) - Different gases have different solubilities. CO₂ is much more
soluble than O₂.
The pressure of the gas (page 11) - According to Henry's law, more gas dissolves at higher
pressure.
The temperature (page 11-12) - The colder the temperature, the more gas is dissolved.
The presence of other solutes (page 12-13) - More substances dissolved in water (like in
seawater) reduces gas solubility compared to freshwater.
Factors Influencing Gas Solubility in Water
The solubility of gases in water is determined by four main physical factors that dictate the difficulty
or ease with which organisms can extract oxygen from their aquatic environment (ZOL2601, Study
Guide. p. 10).
Type of Gas
The chemical nature of the gas itself fundamentally determines its solubility, as different gases
exhibit vastly different solubility coefficients. Carbon dioxide, for instance, is substantially more
soluble in water than oxygen due to its chemical properties and its ability to react with water to form
carbonic acid and subsequent bicarbonate ions (ZOL2601, Study Guide. pp. 10-11, 12).
Pressure of the Gas
The partial pressure of the gas in the gas phase directly influences dissolution, as described by
Henry's law. When the pressure of a gas above water increases, the quantity of that gas dissolving
into the water increases proportionally; conversely, reducing pressure causes gases to leave solution
(ZOL2601, Study Guide. pp. 11, 13).
Temperature
Temperature exerts a strong inverse relationship on gas solubility, wherein colder temperatures
permit greater quantities of gas to remain dissolved in water. As temperature rises, the kinetic energy
of water molecules increases, reducing the capacity of water to retain dissolved gases, which
explains why polar oceans contain more dissolved oxygen than tropical waters (ZOL2601, Study
Guide. pp. 11-12).
Presence of Other Solutes
The concentration of other dissolved substances in water decreases the solubility of gases through
competitive interactions for solvent capacity. Seawater, containing numerous dissolved salts,
demonstrates lower oxygen solubility than freshwater at equivalent temperatures and pressures, as
the dissolved ions effectively reduce the water's capacity to accommodate additional gas molecules
(ZOL2601, Study Guide. pp. 12-13).
