1. Gases

2. Pressure
The pressure of a gas is the force it exerts on a unit surface area
Pressure is measured with a barometer
Measured using mercury in a sealed
Normal is 760mm or in high

3. Pressure Units
The unit for pressure is pascal (Pa) which is a force of 1 Newton exerted on an area of one square meter (N/m3)
1 atm = 101,325 Pa or 101 kPa
Torr are another system created by Evangelista Torricelli who invented the first barometer in 1643

4. Boyle’s Law
P1V1 = P2V2
At a given temperature the volume occupied by a gas is inversely proportional to its pressure
p= k (1/V)
p pressure of gas
V volume of gas
k is a constant needed to make both sides equal

5. Boyle’s Law
So at a given temperature, the product of the pressure and volume of gas must be constant!
If pressure is increased, the volume must decrease
P x V = k

6. Temperature Measured with a thermometer
3 scales: Celsius, Fahrenheit, and KELVIN
Pg. 64

7. Charles’s Law
The volume of a gas increases by 1/273 for each Celsius degree its temperature is increased
is lowest possible attainable temperature or absolute zero

8. Charles’s Law
If we know the volume of a gas at one Kelvin, we can find its volume at any other temperature by the equation.
The equation can also be used to find Kelvin given a known volume

9. Combined Gas Law
Boyle’s law and Charles’s law are combined to make the following equation

10. Combined Gas Law
The temperature and pressure at which the volume of a gas is measured are known as the conditions of measurement.

11. Combined Gas Law
Let’s think about the relationship

12. Example Combined Gas Law
A gas sample occupies 250mL at 27*C and 780 Torr pressure. Find its volume at 0*C and 760 Torr pressure

13. Example Combined Gas Law
A gas sample occupies 250mL at 27*C and 780 Torr pressure. Find its volume at 0*C and 760 Torr pressure
Convert the temperatures to the Kelvin scale by adding 273*C to each
T1= 27*C = 300K
T2 = 0*C = 273K

14. Example Combined Gas Law
A gas sample occupies 250mL at 27*C and 780 Torr pressure. Find its volume at 0*C and 760 Torr pressure
Equation: V2 = V1 x (P1/P2) x (T2/T1)

15. Example Combined Gas Law
A gas sample occupies 250mL at 27*C and 780 Torr pressure. Find its volume at 0*C and 760 Torr pressure
V2 = 250mL x (780 Torr/760 Torr) X (273K/300K)
V2 = 234 mL

16. Each gas would have a volume of 1ft3
Standard Conditions
All gases fill their containers completely!
If we have a mixture of oxygen, nitrogen, and carbon dioxide gases and put the sample into a 1ft3 container, how much by volume of each gas will be present?
Each gas would have a volume of 1ft3

17. Know These!!!! Standard Conditions Temperature Pressure 0*C 760Torr
32*F
29.92 in.
273K
1.000atm or 101kPa
Know These!!!!