Chapter 15- Ideal Gases Flashcards
Mole
The amount of substance that contains as many elementary entities as there are atoms in 12g of carbon-12
N
A
Avogadro’s constant: 6.02 x10^23
Number of molecules or atoms formula
N = n x N
A
number of elementary entities = number of moles x Avogadro’s constant
Ideal gas assumptions
- The gas contains a very large number of particles moving in random directions and with random speeds
- The particles occupy a negligible volume compared with the volume of the gas
- The collisions between particles and the walls of the container are perfectly elastic
- The time of the collisions is negligible compared to the time between collisions
- Electrostatic forces between the particles are negligible except during a collision
Root mean square speed
- Square each speed
- Find the mean of these (c^2 with a line on top)
- Take the square root
Δp from collisions with a container in an ideal gas
Δp = 2mu
Boyle’s Law
p∝1/V or pV = constant
For a constant mass of an ideal gas at a constant temperature
Charles’s Law
V ∝ T
For a constant pressure and constant mass of an ideal gas
Where T is in kelvin
pressure and temperature relationship
p ∝ T or p/T = constant
Combining ideal gas laws
p1V1 p2V2
——- = ——-
n1T1 n1T2
Molar gas constant
R = 8.31J K^-1 mol^-1
Ideal gas equation
pV = nRT
pressure x volume = number of moles x molar gas constant x temperature in kelvin
Average speed comparison
rms speed > mean speed > most probable speed
The difference is greater for lower temperatures
rms formula
pV = 1/3 N m c^2
k
Boltzmann constant
1.38 x 10^-23 J K^-1
