Combined gas law — Science definition
A single relationship that merges the three individual laws: P₁V₁/T₁ = P₂V₂/T₂.
Where it is taught
- The Gas Laws — States of Matter & Gases, Physical Science: Chemistry, Grade 11
In use
Finally, the combined gas law stitches all three together for situations where pressure, volume, and temperature all change at once: P₁V₁/T₁ = P₂V₂/T₂.
The Gas Laws
Questions using combined gas law
Problem 1
A gas occupies 3.0 L at 1.0 atm and 300 K. Using the combined gas law, what volume does it occupy at 2.0 atm and 450 K?
Answer and explanation
2.25 L
Combined gas law: V₂ = V₁ × (P₁/P₂) × (T₂/T₁) = 3.0 × (1.0/2.0) × (450/300) = 3.0 × 0.5 × 1.5 = 2.25 L.
Problem 2
A gas occupies 4.0 L at 1.0 atm and 200 K. Using the combined gas law, what volume does it occupy at 2.0 atm and 300 K?
Answer and explanation
3 L
Combined gas law: V₂ = V₁ × (P₁/P₂) × (T₂/T₁) = 4.0 × (1.0/2.0) × (300/200) = 4.0 × 0.5 × 1.5 = 3.0 L.