s1.5 ideal gases Flashcards
what is an ideal gas?
an ideal gas obeys the following rules under standard temperature and pressure:
1. the volume occupied by ideal gas particles is negligible relative to the volume of the container
2. gaseous particles undergo elastic collisions with each other and the walls of the container. no loss of kinetic energy occurs
3. the particles of an ideal gas are in constant, random, straight-line motion
4. there are no intermolecular forces acting between the particles in an ideal gas
an ideal gas is a hypothetical gas that obeys the gas laws and the kinetic molecular theory
what is a real gas?
a real gas is a gas that deviates from ideal gas behaviour: they have finite measurable volume and intermolecular forces act between the particles.
real gases behave similarly to ideal gases at high temperatures and low pressure
how does a real gas differ from an ideal gas?
under normal conditions, real gases behave very much like ideal gases. real gases differ the most from ideal gases under two conditions: high pressures and low temperatures.
for one mole of an ideal gas, the product of PV/RT is equal to one. for a real gas, PV/RT doesn’t equal one
how does pressure affect PV/RT?
at moderately high pressures, the values of PV/RT are less than one, mainly because of the effects of intermolecular forces - intermolecular forces acting between gaseous particles cause the pressure inside the container to decrease.
at very high pressures, the values of PV/RT are greater than one, mainly because of the effects of molecular volume - the volume of the gaseous particles becomes significant as the space between them decreases
how does temperature affect PV/RT?
at high temperatures, the kinetic energy of the particles overcomes the intermolecular forces between the particles.
at low temperatures, the particles have insufficient kinetic energy to overcome the intermolecular forces between the particles
how can you calculate the molar volume of a gas?
the molar volume of a gas is the volume occupied by one mole of an ideal gas under standard conditions. at STP, one mole of an ideal gas occupies a volume of 22.7 dm³.
volume = moles x 22.7
what is boyle’s law?
boyle’s law states that the volume occupied by a gas i inversely proportional to its pressure at constant temperature. if the pressure of a fixed mass of gas is doubled, then the volume of the gas will halve
PV = k (constant)
P₁V₁ = P₂V₂
what is charles’s law?
charles’s law states that the volume occupied by a gas is directly proportional to its absolute temperature in kelvin at constant pressure. if the temperature of a fixed mass of gas is doubled, the volume also douubles.
V / T = k (constant)
V₁ / T₁ = V₂ / T₂
what is gay lussac’s law?
gay lussac’s law states that the pressure of a gas is directly proportional to its absolute temperature in kelvin at constant volume. if the temperature of a fixed mass of gas is doubled, the pressure of the gas is also doubled.
P / T = k (constant)
P₁ / T₁ = P₂ / T₂
what is the combined gas law?
the combined gas law combines boyle’s law, charles’s law and gay lussac’s law.
P₁V₁ / T₁ = P₂V₂ / T₂
P₁V₁ / T₁ = k (constant)
what is the ideal gas equation?
the ideal gas equation can be rearranged to calculate amount (in mol), volume (in m³), pressure (in Pa), temperature (in K) or molar mass (g mol⁻¹)
PV = nRT
M = mRT / PV
R is the gas constant (8.31 J K⁻¹ mol⁻¹)
