Week 1 Gas Laws Flashcards
What is kinetic theory? What proportion of a gas is made up by gas molecules?
Kinetic theory postulates that gases are made up of submicroscopic particles that are in constant random motion proportional to their energy. Gas molecules form only a small proportion of the total gas volume, most is empty space.
What is generates pressure? What would increase pressure? What is the equation for pressure and the units?
Pressure is generated by the force of molecules hitting against the container walls. Faster or harder collisions (Eg increased temp or increased concentration of gas) will increase the pressure. Pressure= Force / unit area and unit is Pascals (Pa). P= F/A
What is Boyle’s Law?
Boyle’s law states that the pressure of a gas is inversely proportional to its volume at a constant temperature and constant amount of gas: P= 1/ V therefore PV = a constant therefore P1 xV1= P2 xV2
What is Charle’s law?
Charle’s Law states that the volume of a gas is directly proportional to its temperature on an absolute temperature scale and at a constant pressure/ amount of gas. V= T x C Volume= Temp x Constant therefore… V/T= C therefore… V1/T1 = V2/T2
What is the universal gas law/ Ideal gas law?
PV= nRT The pressure x volume = no. of moles of gas x Gas constant x Temp in kelvin
What is partial pressure?
The partial pressure of a gas is the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.
What is Dalton’s law?
Dalton’s law states that the total pressure of a mixture of gases in a fixed volume is proportional to the sum of the individual partial pressures of each gas in the mixture.
What is gas in constant contact with in biological systems? What occurs at the point of contact? What pressure does evaporated water exert?
Gas molecules are in constant contact with water in biological systems. At the point of contact, water molecules evaporate and gas molecules dissolve but there is no reaction between the two. Evaporated water exerts a vapour pressure.
What is reached in closed systems (eg alveoli) when there is a gas/ water interface? What would happen if the volume of gas was unlimited?
An equilibrium is reached in closed system such as alveoli (where there is a constant volume of gas) between the amount of water evaporating and entering the gas phase and the amount of gas entering the liquid phase. If there was unlimited gas volume all water would evaporate as no equilibrium could be reached.
What is it called when water reaches an equilibrium between its liquid and gas phase?
This is called the saturated vapour pressure (SVP).
Define Saturated vapour pressure
The pressure of a vapour which is in equilibrium with its liquid phase.
When is the boiling point of a gas reached?
The boiling point of a gas is reached when its saturated vapour pressure is equal to atmospheric pressure (1 atmosphere).
What is saturated vapour pressure dependent on?
Saturated vapour pressure is dependent on the temperature only. If you increase the T you increase kinetic energy and the number of molecules able to leave the liquid phase and enter the gas phase.
What is Henry’s Law? What is the proportionality constant for this equation representing?
Henry’s Law states that at a constant temperature the amount of gas that will dissolve in a particular volume of solvent is directly proportional to the partial pressure of that gas overlying the gas/ liquid interface (or directly proportional to the partial pressure of that gas in equilibrium with that liquid). The proportionality constant for this equation represents the Solubility of that gas in that particular liquid.
Define solubility What is it dependent on?
Solubility is defined as the ability of a certain solute to dissolve in a certain volume of solvent at a constant temperature. It is defined as the amount of solute per volume of solvent and is measured at saturation point where the addition of more solute results in precipitation. The solubility of a substance in a particular solvent is dependent on the individual properties of the solute in that solvent.
Define the solubility of gas What two factors affect the solubility of a gas in a liquid?
The solubility of a gas in a given volume of liquid represents its ability to dissolve in that liquid and is constant for specific gas and liquid, depends on the physical properties. Temperature affects solubility as the higher the temperature the more kinetic energy gas molecules have, pushing the equilibrium towards evaporation. Pressure affects solubility of gas as it relates to Henry’s law- the higher the partial pressure of a gas over a liquid interface the more gas will dissolve in that given volume of liquid.
What is Gas Tension?
Gas molecules entering water exert a pressure- termed the gas tension. The gas tension of a particular gas entering a liquid is proportional to the partial pressure of that gas in equilibrium with that liquid. (Henry’s Law). Gas tension represents the ease with which gas molecules will leave the liquid phase. It is not a measure of the physical amount of gas in the liquid but the partial pressure of that gas within the liquid. Represented in kilopascals e.g. PaCO2- 5.3 kPa in alveoli.
What is the content of gas in a liquid? What does the gas content depend on?
The content of a gas is the actual physical amount of gas contained within a certain volume of liquid. It is represented by the volume of gas contained within a certain volume of that liquid e.g. O2 mls/ L of blood. It depends on both the solubility of the gas and the partial pressure of the gas in equilibrium with the liquid.
What does diffusion require? Define gaseous diffusion
Diffusion requires a concentration gradient Gaseous diffusion is by the random movement of gas particles and results in net transfer of gas particles from an area of high concentration to an area of low concentration.
Describe the general structure of an alveolus
Each alveolus is a thin walled hexagonal structure surrounded by a capillary plexus and supplied by a tiny bronchiole called an alveolar duct.
How is blood able to carry O2/CO2 and transfer it from tissues/ lungs?
This is due to the properties of haemoglobin in RBC’s.
How does the O2 content of blood reach equilibrium? What is total O2 content of the blood made up of?
Haemoglobin fully saturates all its binding sites with O2 and reaches equilibrium before the tension of blood can reach equilibrium. Therefore the total O2 content is made up of both reacted O2 with haemoG and dissolved O2 in the plasma.
What 3 properties does the final O2 content of blood at equilibrium depend on?
1) the gas tension 2) the solubility of O2 in blood 3) the avidity of haemoglobin for O2.
Where does gas exchange take place and by what transport mechanism?
What does this transport mechanism depend on?
Gas exchange takes place at the alveolar membrane and by diffusion.
Diffusion is dependent on a concentration gradient.
