Gas Law Variables :

1
Gas Law Variables

• P Pressure
• V Volume
• T Temperature
• n of moles

2
Boyles Law

• P and V of a gas at constant T are inversely
  proportional to each other.
• PVk (k is a const.)

3
Boyles Law

• P1V1 k P2V2

4
Inversely Proportional

• as one increases, the other decreases

5
Problem

• The V of air in a bicycle pump 2 L and the P
  1 atm. If the air is compressed to 0.5 L, what
  is the new P?

4 atm
6
Problem

• P1 99.0 kPa
• V1 300 mL
• P2 188 kPa
• V2 ?

158 mL
7
STP

• Standard Temperature and Pressure
• T 0 C 273 K
• P 1 atmosphere

8
Charles Law

• V and T of a gas at constant P are directly
  proportional to each other.
• V ? T k

9
Charless Law

• V1
• T1

V2 T2
k
10
Gas Law Units

• Temperature units MUST use the Kelvin scale (K).
• P and V units can be any weve used, as long as
  only one P and one V scale is used per problem.

11
Absolute Zero
12
Absolute Zero (0 K)

• T at which a gas would have NO volume and NO
  motion
• 0 K -273.15 C

13
Problem

• The volume of air in a balloon 2 L and its
  temperature 280 K. After heating the air to
  30?C, what does the new V?

2.16 L
14
Problem

• V1 3.00 L
• T1 80.0 C
• T2 30.0 C
• V2 ?

2.58 L
15
Gay-Lussac

• P and T of a gas at constant V are directly
  proportional to each other.
• P ? T k

16
Gay-Lussacs Law

• P1
• T1

P2 T2
k
17
Problem

• If the pressure of a gas is 1 atm at T 35ºC,
  what is its new pressure at T 25ºC?

0.967 atm
18
Temperature Units

• MUST be in Kelvins
• ºC 273 K

19
Avogadros Principle

• Equal volumes of gases at the same T and P
  contain equal numbers of particles.
• V ? n k

20
Avogadros Principle

• V1
• n1

V2 n2
k
21
Gas Molar Volume

• The volume of 1 mole of gas.
• 22.4 L/mole at STP

22

• Direct Proportion (variation) y kx
• Straight line graph. Variables change in same
  direction.

23

• Inverse Proportion (variation) y kx
• Curved-line graph. Variables changein opposite
  directions.