Properties of Gases:

1. Temperature (in K)

2. Volume (L, mL)

3. Pressure

P = Force/area

N/m² = Pa (Pascal)

atmosphere = atm

1 atm = 101,325 Pa

1 mm Hg = 1 torr

1 atm = 760 torr (know this)

1 bar = 105 Pa = 0.9869 atm

4. Moles of atoms or molecules in the gas

The state of a gas can be described in terms of these four properties.

The Gas Laws

Dalton's Law of Partial Pressures

P_tot = P₁ + P₂ + ... + P_n

The total pressure of a mixture of gases is equal to the _____ of the partial pressures of the individual gases in the mixtures.

Boyle's Law

Some experimental data:

Plot is not linear, but there appears to be an inverse relationship between P & V. Let's calculate 1/V:

Plotting P vs 1/V:

This relationship is linear so P = k(1/V) or PV = k = slope of line. Thus:

P₁V₁ = P₂V₂ = k at constant T

This is known as Boyle's Law.

The ______________ is constant. k is a proportionality constant.

For a gas at constant temp., pressure and volume are ____________________.

Charles' Law

Now let's look at volume & temperature:

Plotting V vs T:

This gives a linear plot,

so V = cT at constant P

This is known as Charle's Law.

V₁/T₁ = V₂/T₂ = c

The ___________ is a constant.

For a gas at constant pressure, volume and temperature are _____________________.

Avogadro's Law

V = an where n = moles of gas

For a gas at constant temp. and pressure, the volume is __________________ to the number of moles of gas.

The Ideal Gas Law

P is proportional to 1/V

V is proportional to T

V is proportional to n

R = 0.08206 L atm/(mol K)

Putting all these proportionalities together we get the equation:

PV = nRT

where R is the universal gas constant and is a proportionality constant.

The ideal gas law is an empirical equation which works for any gas if P is not too high and T is not too low.

PV = nRT can be derived from the kinetic molecular theory of gases.