1. Chapter Gases
6.6
The Combined Gas Law

2. Combined Gas Law
The combined gas law uses Boyle’s Law, Charles’ Law, and Gay-Lussac’s Law (n is constant).
P1 V1 = P2 V2
T1 T2

3. Learning Check
A gas has a volume of 675 mL at 35°C and atm pressure. What is the volume(mL) of the gas at -95°C and a pressure of 802 mm Hg (n constant)?

4. Solution Data Table Conditions 1 Conditions 2
T1 = 308 K T2 = -95°C = 178K
V1 = 675 mL V2 = ???
P1 = 646 mm Hg P2 = 802 mm Hg
Solve for V2
V2 = V1 x P1 x T2
P T1
V2 = mL x mm Hg x 178K = mL
802 mm Hg x 308K

5. Combined Gas Law Calculation
A sample of helium gas has a volume of L, a pressure of atm and a temperature of 29°C. At what temperature (°C) will the helium have a volume of 90.0 mL and a pressure of 3.20 atm (n is constant)?
1. Set up Data Table
Conditions 1 Conditions 2
P1 = atm P2 = atm
V1 = L (180 mL) V2 = 90.0 mL
T1 = 29°C = 302 K T2 = ??

6. Combined Gas Law Calculation (continued)
2. Solve for T2 P1 V1 = P2 V2
T1 T2
T2 = T1 x P2 x V2
P V1
T2 = 302 K x atm x mL = K
0.800 atm mL
T2 = 604 K = °C