som week 9

Question 1

give the ideal gas equation

Answer 1

pV = nRT

Question 2

give the pressure equation for a liquid

Answer 2

p = ρhg

ρ = density of liquid 
h = height of liquid 
g = gravitational speed 9.8m/s

Question 3

give the equation for changing conditions of a fixed gas

Answer 3

p₁V₁/T₁ = p₂V₂/T₂

Question 4

give the equation for the total pressure of a mixture of gases

Answer 4

total pressure = sum of partial pressures of each gas

ptotal = pa + pb + pc +…

Question 5

give the equation for mole fraction

Answer 5

mole fraction of gas A for example is the moles of gas A over the total moles in the mixture

𝑥a = na/ntotal

Question 6

give the equation for partial pressure of a particular gas

Answer 6

partial pressure = mole fraction x total pressure

pa = 𝑥a ptotal

Question 7

average kinetic energy of gas molecules is proportional to?

Answer 7

average kinetic energy is proportional temperature

Question 8

what is the symbol, units and equation for root mean square speed

Answer 8

Vrms or c in m/s

c = √(3RT/M)

M - molar mass in kg/mol

Question 9

describe the distribution of gas speeds

Answer 9

Boltzmann distribution/bell shaped curve

• peak of bell curve represents the most probable speed
• fewer molecules have extreme high and low speeds

Question 10

as molar mass changes, what happens to

• the speed of gas molecules?
• the distribution curve?

Answer 10

higher M = lower speed, steeper curve

lower M = faster speed, broader curve

Question 11

as temperature changes, what happens to

• the speed of gas molecules
• the distribution curve

Answer 11

higher T = faster speed, broader curve

lower T = slower speed, steeper curve

Question 12

define effusion

what is rate of effusion proportional to

Answer 12

gas molecules pass thru tiny holes in a porous barrier

rate of effusion ∝ 1/√M
inversely proportional to molar mass square rooted