1. Dalton’s, Boyle’s and Charles’s Laws
Day 2 – Notes
Unit: Gas Laws
Dalton’s, Boyle’s and Charles’s Laws

2. After today you will be able to…
Describe Dalton’s law of partial pressures and calculate Ptotal or a partial pressure
Explain the effect on gas properties using Boyle’s and Charles’s laws
Calculate an unknown pressure, temperature, or volume by solving algebraically

3. Recall, gas pressure results from collisions of gas particles.
Gas pressure depends on the amount of gas and the KE of its particles.
Since particles in a mixture of gases at the same temperature contain the same average KE, the kind of particle is unimportant.

4. Example: Composition of Dry Air
Component
Volume
Partial Pressure
Nitrogen
78.08%
79.11 kPa
Oxygen
20.95%
21.22 kPa
Carbon dioxide
0.04%
0.04 kPa
MISC gases
0.93%
0.95 kPa
Total
100.00%
kPa

5. “The total pressure of a mixture of gases is equal to the sum of the individual (partial) pressures.”

6. Dalton’s Law of Partial Pressures
Units of pressure must match!
Ptotal= P1 + P2 + P3…

7. Example: Dalton’s Law
What is the total pressure for a mixture of O2 and CO2 if PO2= atm and PCO2= 423mmHg. PO2= 0.719atm PCO2= 423mmHg
760mmHg x =
546mmHg
1atm
Ptotal=546mmHg + 423mmHg
Ptotal=969mmHg

8. Boyle’s Law: Pressure and Volume
Robert Boyle was the first person to study the pressure-volume relationship of gases.
In 1662 Boyle proposed a law to describe this relationship.

9. “For a given mass of a gas at constant temperature, the volume of a gas varies inversely with pressure.”

10. Boyle’s Law: Pressure and Volume
We can simplify this relationship by the formula: Where, P1, P2 = pressure in any unit (atm, kPa, mmHg), BUT they must match! V1, V2 = volume in any unit (usually, L or mL), BUT they must match!
P1 V1 = P2 V2

11. Boyle’s Law: Example P1 V1=P2 V2 V2 180L =
A gas has a volume of 30.0L at 150 kPa. What is the volume of the gas at atm? P1= V1= P2= V2=
1 atm
150 kPa x
P1 V1=P2 V2 =
1.5 atm
101.3 kPa
30.0L
0.252 atm ?
(1.5 atm)
(30.0L) =
(0.252 atm)
(V2) V2 =
180L

12. Charles’s Law: Temperature and Volume
Jacques Charles studied the effect of temperature on volume of a gas at constant pressure.
In 1787 Charles proposed a law to describe his observations.

13. “For a given mass of a gas, at constant pressure, the volume of the gas is directly proportional to its temperature in Kelvin.”

14. Charles’s Law: Temperature and Volume
We can simplify this relationship by the formula: Where, V1, V2 = volume in any unit (L or mL), BUT they must match! T1, T2 = temperature is always in Kelvin! (Recall, just add °C)
V1 V2
T1 T2 =

15. Charles’s Law: Example
A gas has a volume of 4.0L at 27°C. What is its volume at 153°C?
V1=
T1=
V2=
T2=
V1 V2
T1 T2
4.0L =
27°C +273= 300K ?
153°C+273= 426K
(4.0L)
(V2) =
(300K)
(426K) V2 =
5.7L

16. Questions? Complete WS 2