Dalton’s Law & Boyle’s Law
Dalton’s Law of Partial Pressure
• The total pressure in a
system is equal to the sum
of the pressures of each
gas inside.
• Ptotal= P1 + P2 + P3 + …Pn
Remember
me?
In a closed system, the partial pressures of three gases were 1.5 atm.,
2.0 atm., and .75 atm. What is the pressure of the system?
Ptotal= P1 +P2 + P3
Ptotal= 1.5atm + 2.0 atm + .75 atm
Ptotal= 4.25atm
In a closed system, there are four gases present. The pressure of the
first gas is 796 mmHg. The Second gas has a pressure of 755 mmHg;
and the third gas has a pressure of 760 mmHg. What is the pressure
of the fourth gas if the total pressure of the system is 3000 mmHg?
Ptotal= P1 +P2 + P3 + P4
3000mmHg= 796mmHg + 755mmHg + 760mmHg + P4
3000mmHg = 2311mmHg + P4
689mmHg= P4
Boyle’s Law
• Pressure and volume
have an inverse
relationship
• Can be explained with
Kinetic Molecular
Theory
– Decreasing volume
increases the number of
molecules per unit
volume, leading to more
collisions
P1V1= P2V2
•
•
•
•
P1 = initial pressure
V1= initial volume
P2= final pressure
V2= final volume
A sample of neon to be used in a neon sign has a volume of
1.51 L at a pressure of 635 torr. Calculate the volume of the
gas after it is pumped into the glass tubes of the sign, where
it shows a pressure of 785 torr.
P1V1= P2V2
1.51x635= 785V2
958.85= 785V2
785
785
1.22L= V2
A sample of oxygen that occupies 1.00 × 106 mL at 575 mm
Hg is subjected to a pressure of 1.25 atm. What will the final
volume of the sample be if the temperature is held constant?
1atm= 760 mmHg
P1V1= P2V2
760mmHg = 575mmHg
1atm
x
0.76x1.00x106= 1.25V2
575= 760 x
760 760
0.76atm= x
7.60x105= 1.25V2
1.25
1.25
6.08x105 mL= V2
A gas has a pressure of 1.26 atm and occupies a volume of
7.40 L. If the gas is compressed to a volume of 2.93 L, what
will its pressure be, assuming constant temperature?
P1V1= P2V2
1.26x7.40= P2x2.93
9.32= P2x2.93
2.93 2.93
3.18L= V2