Matter

Gas Laws

Amount = moleTemperature = Kelvin

Volume = LitersPressure = mm Hg, atm

Gas laws are mathematical equations that relate the amount, pressure,

temperature, and volume of a gas.

A barometer is a device used to measure atmospheric pressure.

Atmospheric pressure is expressed in terms of the height of the barometer’s mercury column, usually in millimeters of mercury(mm Hg).

1 mm Hg = 1 torr1 atm = 760 mm Hg = 760 torr = 14.7 psi

Pressure

Laws, Formulas, and PicturesThursday, November 15, 20073:09 PM

CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 1

Boyle's Law

P1

V

P1 V1 P2 V2

or

Boyle’s law: the volume of a fixed amount of gas is inversely proportional

to the pressure applied to the gas if the temperature is kept constant.

Charles's Law

V T

V1

T1V2

T2

or

Charles’s law: the volume of a fixed amount of gas is directly proportional

to its Kelvin temperature if the pressure is kept constant.

CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 2

Avogadro's Law

Avogadro’s law: the volume of a gas is directly proportional to the number

of moles if the pressure and temperature are kept constant.

V n

V1

n1V2

n2or

Which Formula Do I Use?

Law Variables Constants

Boyle’s P, V n, T

Charles V, T n, P

Combined P, V, T n

Avogadro V, n P, T

Ideal P, V, n, T none

CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 3

Dalton's Law of Partial Pressures

Dalton’s law: the total pressure exerted by a mixture of gases is equal to

the sum of the partial pressures of the individual gases.

PTotal P1 P2 P3 ...

PTotal P1 P2 P3 ...

The total pressure exerted by a mixture of O2, N2, and He gases is 1.50 atm.

What is the partial pressure, in atmospheres, of the O2, given that the partial pressures of the N2 and He are 0.75 and 0.33 atm, respectively.

PO2 PTotal PN2 PHe 1.50 0.75 0.33 0.42atm

CHEM 1151 - Organic & Biological Chemistry.one (On 1-6-2008).one (On 6-5-2008) Page 4