Gases & Atmospheric Chemistry
Charles’ & Gay-Lussac’s Gas Laws
Unit 5
Review

What is the relationship between pressure and volume?

Can you tell me the name of the Law for this
phenomenon?

Who can come and write the Law on the board?

Let’s Practice!
Kelvin Temperature Scale

Absolute Zero = believed to be the lowest
possible temperature


= -273ºC


Temperature at which a volume of gas would be zero
0 K = - 273 oC ( -273.15 oC to be more precise)
Kelvin Temperature Scale = a temperature
scale with zero kelvin (0 K) at absolute zero
and the same size divisions as the Celsius
temperature scale
Lord Kelvin used Charles’
Law to determine this
Kelvin Scale
To convert:
TK = ToC + 273
e.g.
1. Convert to Kelvin scale
a) 25 oC
b) - 58 oC
2. Convert to Celsius scale
a) 475 K
b) 17 K
100 0C
373 K
0 0C
273 K
-273 0C
0K
Absolute Zero
As temperature decreases the volume of a gas
decreases (or the pressure drops, if you keep
the volume the same)
 We can deduce how cold you would have to
make the gas, in order for the volume to be zero
(-273°C or 0K)
 A gas cannot have a zero volume therefore
absolute zero is an unattainable limit

Relationship: Volume & Temp.
Regardless of gas,V = 0 when T= - 273 oC
Charles’s Law
Relationship: Volume & Temp.

As temperature increases volume increases
V  T (direct proportion)
As temperature increases volume increases
Charles’s Law
Relationship: Volume & Temp.

Charles’s Law = the volume of a gas varies directly
with its temperature in kelvin, if the pressure and the
amount of gas are constant
v = kT



v = volume (L)
T = Temperature in Kelvin (K)
k = constant (slope of the straight line in the graph)
Charles’s Law
Relationship: Volume & Temp.

Charles’s Law can be written comparing any
two sets of volumes and temperatures:

k = v1/T1 and k = v2/T2

Therefore:
v1/T1 = v2/T2
(Charles’s Law)
Charles’ Law
Sample Problems:
1.
75 mL of dry hydrogen gas at 22 oC is drawn into a syringe. If the
temperature is raised to 125 oC, keeping the pressure constant, what
volume will this same mass of hydrogen gas occupy?
(ans: 1.0 x 102 mL)
2. A balloon filled with dry He(g) has a volume of 3.75 L at 25 oC. The same
balloon is placed in a freezer and the volume of the balloon now is 3.05 L.
Calculate the temperature (in oC) of the freezer.
(ans: -31 oC)
Practical Applications

Should you throw an aerosol can into a fire?
What could happen?

When should your automobile tire pressure
be checked?
Gay-Lussac’s Law
Relationship: Pressure & Temp.
Graphically: P  T (direct proportion)
Gay-Lussac’s Law
Relationship: Pressure & Temp.
Gay-Lussac’s Law
Relationship: Pressure & Temp.

Pressure & Temperature Law = the
pressure exerted by a gas varies directly with
the absolute temperature if the volume and
the amount of gas remain constant
p1/T1 = p2/T2
Gay-Lussac’s Law
Sample Problems:
1.
Assuming that room temperature is 22 oC, to what temperature must
a given mass of gas be raised such that its pressure is doubled?
(ans: 317 oC)
2.The pressure gauge reading on a cylinder of oxygen gas is 8.5x103 kPa, at
22 oC. What will be the pressure if the cylinder is placed in boiling
water?
(ans: 1.1 x 104 kPa)
Summary
•
•
•
•
Boyle’s Law (PiVi=PfVf)
o P↑V↓ or P↓V↑
Charles Law (Vi/Ti=Vf/Tf)
o V↑T↑ or V↓T↓
Gay-Lussac’s Law (Pi/Ti=Pf/Tf)
o P↑T↑ or T↓T↓
Eventually leads to combined gas law
o (PiVi/Ti=PfVf/Tf) next chapter.