1

GAS LAWS

Kinetic Theory1. All matter is made up of small particles.

2. The particles are in constant motion.

3. The collisions between particles are elastic

2

GAS LAWS

Gas is described in three quantities1. Temperature (K)

2. Volume (m3) (l) (cc)

3. Pressure (Pa) (N/m2) (torr) (mm of mercury)

Pressure is defined as force per unit areaP = F/A = N/m2

3

Gas Laws

Standard Atmospheric Pressure - The atmospheric pressure at sea level 1 Atmosphere 101 kPa 1.01 x 105 Pa 760 mm 760 torr 14 lb/in2

4

Gas Laws

Barometer- A device

for measuring the

pressure of the

atmosphere.

5

Gas Laws

Boyle’s Law- The volume occupied by a gas varies inversely with the applied pressure at constant temperature.

Inverse Proportion - As the pressure increases, the volume decreases. As the pressure decreases, the volume increases

6

7

Volume Vs Pressure

(10,225)

(20, 112.5)

(30,75)(50,45) (70,32)

8

Gas Laws

Charles’ Law - All gases expand at the same amount for a given temperature change at constant pressure.

Direct Proportion - As the temperature increases, the volume increases. As the temperature decreases, the volume decreases.

9

Gas Laws Charles’ Law established:

Absolute zero 0 K = -273°C, A theoretical value where the gas has no volume.

V1/V2 = T1/T2

All values for temperature must be in Kelvin.

10

(50,1.18)(100,1.37)

(150,1.55)

(200,1.73)

2

2

1

1

t

vk

t

v

11

Gas Laws

Combined Gas Law P1V1

T1

P2V2

T2

If the pressure is constant V1

T1

V2

T2

If the volume is constant P1

T1

P2

T2

If the temperature is constant P1V1 P2V2

12

Gas Laws

A gas tank has 13 liters of gas at -10°C. How much gas will be in the tank at 30° C?

V1 = 13 lT1 = -10°C = 263 KT2 = 30° C = 303 K

V1/V2 = T1/T2

V2 =V1T2/T1

V2 =(13 l)(303 K) /(263 K)

V2 =15 l

13

Gas Laws

The air pressure of a truck tire is 30 lb/in2 at -3º C. What will theAir pressure be at 27 °C?

P1 = 30 lb/in2+14.7 lb/in2

T1 = -3°C = 270 KT2 = 27° C = 300 K

P1/P2 = T1/T2

P2 =P1T2/T1

P2 =(45 lb/in2)(300 K) /(270 K)

P2 =50 lb/in2 P2 =35 lb/in2

14

Gas Laws

A 20 liter sample of argon at 273 K is at atmospheric pressure. The temperature is lowered to 77 K, while the pressure is increasedto 145 kPa. What is the new volume of the gas?

P1 = 101 kPaV1 = 20 LT1 = 273 KT2 = 77 KP2 = 145 kPa

P1V1

T1

P2V2

T2

V2 P1V1T2

P2T1

V2 (101kPa)(20L)(77K)

(145kPa)(273K)V2 3.9 L

15

Gas Laws

A tank of helium gas used to inflate toy balloons is at 15.5 x 106 Papressure at 293 K and has a volume of 0.020 m3. How large of a balloon would it fill at a pressure of 1 atmosphere and 323 k?

P1 = 1.55 x 107 PaV1 = 0.020 m3

T1 = 293 KT2 = 323 KP2 = 1 atm = 1.01 x 105 Pa

P1V1

T1

P2V2

T2

V2 P1V1T2

P2T1

Pa)(293K)(1.01x10

)(323K)Pa)(0.020m(1.55x10V

5

37

2 V2= 3.4 m3