gaseous state Flashcards
what is this
assumptions for ideal gas equation:
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- Gas particles have negligible volumes compared to the total volume occupied by the gas
- There are negligible intermolecular forces of attraction between gas particles
- Gas particles are in constant random motion
- The collisions between gas particles and with the walls of the container are perfectly elastic
Conditions leading to deviation from ideal gas behaviour
low T-> there are significant intermolecular forces of attraction between molecules, leads to loss in avg KE of molecules during collisions ie. collisions are inelastic
high Pa-> volume of gas particles is significant compared to that of the container(P proportional to 1/V)
When pressure is high
gases have larger molar volume (Vm) than an ideal gas
At high pressures, the average separation between the molecules decreases to the extent where repulsive forces dominate.
The repulsive forces help to drive the gas particles apart, causing an increase in molar volume (Vm) relative to that of an ideal gas. Gas is expected to be less compressible than an ideal gas
Dalton’s Law of Partial Pressures
In a mixture of inert gases, at constant V and T, total Pa of the mixture is the sum of the partial pressures of the constituent gases
What is the significance of the equation:
Pa =(Xa)(Pt)? , where Xa = Na/Nt
a gas contribution to the total pressure in a mixture of ideal gases depends only on its relative amount, regardless of its mass and identity
When pressure is low to intermediate
Gases have smaller molar volume than an ideal gas cuz significant intermolecular forces of attraction decreases the molar volume relative to that of an ideal gas
When temperature is low
Deviation of real gas from ideality increases.
As T decreases, avg KE of gas particles decreases. Intermolecular forces of attraction become significant as the gas particles possess lower energy and become closer together. Lower the T, bigger the dip
A sealed 1 dm3 vessel, X, contains pure oxygen gas at 25 °C and 100 kPa.
When the vessel is warmed to 35 °C the new pressure of the oxygen gas is 103.4 kPa.
A sealed 2 dm3 vessel, Y, contains 1 dm3 oxygen gas and 1 dm3 of distilled water
saturated with oxygen at 25 °C and a pressure of 100 kPa.
The temperature of vessel Y is increased to 35 °C and a new equilibrium is established.
–> Suggest why the actual value for the pressure recorded in vessel Y was slightly different from the value calculated by this method. Assume oxygen gas behaves as an ideal gas under these conditions.
In the sealed vessel, an equilibrium is established between water vapour (due to evaporation) and liquid water as well. The pressure recorded in the vessel is the sum of the partial pressures of oxygen and water vapour. The volume of distilled water would also be less than 1 dm3 when an equilibrium is established between water vapour and liquid water. The moles of oxygen gas in the distilled water at saturation decreases and more oxygen gas will escape from the water sample.
