1. Basic Chemistry Chapter 11 Gases Chapter 11 Lecture
Fourth Edition
Chapter Gases
11.6 Combined Gas Law
Learning Goal Use the combined gas law to find the final pressure, volume, or temperature of a gas when changes in two of these properties are given and the amount of gas is constant.

2. Combined Gas Law
Combined gas law
incorporates all pressure-volume-temperature relationships for gases previously studied
is useful for studying the effect of changes in two of these variables on the third variable, while the amount remains constant

3. Summary of Gas Laws

4. Learning Check
Helium gas has a volume of L, a pressure of atm, and a temperature of 29 °C. At what temperature (°C) will the gas have a volume of 90.0 mL and a pressure of 3.20 atm?

5. Step 1 Organize the data in a table of initial and final conditions.
Solution
Helium gas has a volume of L, a pressure of atm, and a temperature of 29 °C. At what temperature (°C) will the gas have a volume of 90.0 mL and a pressure of 3.20 atm?
Step 1 Organize the data in a table of initial and final conditions.
Conditions 1
Conditions 2
P1 = atm
P2 = 3.20 atm
V1 = L (180. mL)
V2 = 90. mL
T1 = 29 °C = 302 K
T2 = ?

6. Solution
Helium gas has a volume of L, a pressure of atm, and a temperature of 29 °C. At what temperature (°C) will the gas have a volume of 90.0 mL and a pressure of 3.20 atm?
Step 2 Rearrange the gas law equation to solve for the unknown quantity.

7. Solution
Helium gas has a volume of L, a pressure of atm, and a temperature of 29 °C. At what temperature (°C) will the gas have a volume of 90.0 mL and a pressure of 3.20 atm?
Step 3 Substitute values into gas law equation and calculate.

8. 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 mmHg?

9. Step 1 Organize the data in a table of initial and final conditions.
Solution
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 mmHg?
Step 1 Organize the data in a table of initial and final conditions.
Conditions 1
Conditions 2
P1 = atm
P2 = 802 mmHg = 1.06 atm
V1 = mL
V2 = ?
T1 = 35 °C = 308 K
T2 = −95 °C = 178 K

10. Solution
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 mmHg?
Step 2 Rearrange the gas law equation to solve for the unknown quantity.

11. Solution
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 mmHg?
Step 3 Substitute values into gas law equation and calculate.