Gas laws

Question 1

Mole fractions:

Answer 1

The number of moles of a gas divided by the total moles of a gas in a mixture. Also works with partial pressures, and partial volumes)

n_gas/n_total

Question 2

Standard temperature and pressure(STP):

Answer 2

Standard:

Temperature= 273 Kelvin

Pressure= 1 atmospere/760 torr

At STP, 1 mol of any gas occupies 22.4 Liters

Question 3

Kinetic molecular theory:

Answer 3

Attempts to describe the properties of gases based off a number of assumptions.

Question 4

Kinetic molecular theory assumptions:

Answer 4

1. Assumes that gases are made up of individual molecules that are in constant, random, rapid motion.
2. The molecules themselves are soccupy no volume (thus leaving only the space beween the molecules as the volume occupied by the gas)
3. These particles all have the same mass.
4. The molecules neither attract, or repel eachother.
5. These molecules are constanlty bouncing off of eachother and the walls of their container in perfect eleastic colisions (no energy is lost).
6. The colisions against the walls of the container resulats in pressure.
7. All gases at the same temperature have the same average kinetic energy. Heating increases the kinetic energy and cooling decreases it.

Question 5

Graham’s Law:

Answer 5

At a constant temperature, the rate of effusion of a gas is inversely proportional to the square root of its formula weight. (The heavier the formula weight, the slower the rate of defusion.) Also works for densities.

v= rate of defusion of gas

m= formula weight of gas

Replace “m’s” with “d’s” for density.

Question 6

Dalton’s Law of partial pressures:

Answer 6

The total pressure (or volume) of a mixture of gases is equal to the sum of all of the partial pressures (or partial volumes) of the individual gases.

P_T= p₁+p₂+p₃+…

V_T= v₁+v₂+v₃+…

p_gas=n_gas/n_total•P_T

p_gas= partial pressure for the gas in question

n_gas= moles of the gas in question

n_T= total moles of all gases in the mixture

P_T= total pressure

Question 7

Charle’s Law:

Answer 7

Volume of a gas is directly proportional to the absolute temperature at a constant pressure.

V/T=a constant pressure

V₁/T₁=V₂/T₂

Question 8

Combined gas Law:

Answer 8

Combining Boyle’s law and Charle’s law we get:

PV/T= Constant

P₁V₁/T₁=P₂V₂/T₂

Question 9

Boyle’s Law:

Answer 9

Pressure is inverslely proportional to volume

PV= a constant temp

P₁V₁=P₂V₂

P₁=P₂V₂/V₁

V2=P₁V₁/P₂

Question 10

Ideal gas law and weight of gas

Answer 10

The n in the ideal gas law represents the number of moles of a gas. It can be expressed as:

weight of gas•1/M=n

M=the formula weight of the gas in grams per mole.

So the ideal gas law formula can be rewritten:

PV=weight of gas•(RT/M)

OR

M=(weight of gas•RT)/PV

Question 11

Universal gas constant

Answer 11

If V is expressed in liters and P is expressed in atmospheres, then R=.082

If V is expressed in liters and P is expressed in torr, then R=62.4

If V is expressed in milliliters and P is expressed in torr, then R=62,400

Question 12

Ideal gas Law:

Answer 12

Adds in the universal gas constant, R and the number of moles, n, to the combined gas equation.

PV=nRT