Ideal Gas

Question 1

ideal gas law (equation of state)

Answer 1

an ideal gas is a gas that obeys the equation of state pV = nRT at all pressures, volumes and temperatures

where
p is pressure of the gas in pascals,
V is volume of the gas in cubic metre,
n is amount of gas in moles,
R is molar gas constant 8.31 J mol−1 K−1
T is the thermodynamic temperature in Kelvin.

Question 2

how does pressure arise

Answer 2

•gas particles are in constant random motion & experience changes in momentum when colliding with inner walls of container
•by N2L, gas particle experiences force due to rate of change in momentum during collision
•by N3L, there’s a force exerted on wall that’s equal in magnitude & opposite in direction to force exerted on gas particle
•many forces averaged to give constant force
• P=F/A

Question 3

assumptions behind kinetic theory of gases

Answer 3

1. gas molecules are hard, elastic identical spheres
2. large number of gas molecules are in continuous random motion
3. no intermolecular forces except during collision
4. total volume of molecules negligible compared to volume of container
5. time of collision negligible compared to time between collisions

Question 4

why change in U directly proportional to change in T in ideal gases

or

why change in KE = change in U in ideal gases

Answer 4

• IE is sum of KE due to random motion of distribution of particles and PE due to IMF btwn particles
• in ideal gases, no IMF so no PE
• hence IE is solely KE of particles & KE proportional to T