Combined Gas Law Calculator

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In this Combined Gas Law Calculator, we will show you how to calculate pressure, volume, or temperature in just a few seconds.

We will also help you understand the combined gas law definition, and the combined gas law formula while we’re at it.

What is the combined gas law?

How to calculate real-world problems using the combined gas law? Find all the answers here! With our step-by-step examples, you will master the concept effortlessly.

Combined Gas Law Calculator

📘 Combined Gas Law Formula

The Combined Gas Law relates pressure, volume, and temperature of a gas when the number of moles is constant.

(P₁ × V₁) / T₁ = (P₂ × V₂) / T₂

– P₁, P₂ → Initial & final pressure (atm)
– V₁, V₂ → Initial & final volume (L)
– T₁, T₂ → Initial & final temperature (Kelvin)

⚠️ Always convert temperatures to Kelvin: T(K) = T(°C) + 273.15

📌 Real-World Applications

Scuba Diving

Helps divers calculate safe tank pressure changes when ascending or descending underwater.

Aerospace Engineering

Used to study how gas pressure and volume vary in aircraft cabins at different altitudes.

Car Engines

Helps engineers analyze combustion chambers where pressure, volume, and temperature change rapidly.

Weather Balloons

Predicts how balloons expand and pressure changes as they rise through the atmosphere.

Food Packaging

Explains why sealed chips packets expand when carried to higher altitudes.

✍️ Example Problem

Problem: A 2.5 L gas at 1 atm and 25 °C is heated to 100 °C while the pressure increases to 1.2 atm. What is the final volume?

Step 1 – Given Data:
V₁ = 2.5 L
P₁ = 1 atm
T₁ = 25 °C = 298.15 K
P₂ = 1.2 atm
T₂ = 100 °C = 373.15 K
V₂ = ?

Step 2 – Formula:
(P₁ × V₁) / T₁ = (P₂ × V₂) / T₂

Step 3 – Rearrange for V₂:
V₂ = (P₁ × V₁ × T₂) / (P₂ × T₁)

Step 4 – Substitute Values:
V₂ = (1 × 2.5 × 373.15) / (1.2 × 298.15)

Step 5 – Calculate:
V₂ ≈ (932.87) / (357.78) ≈ 2.61 L

✅ Final Answer:
The final volume of the gas is 2.61 L.

📋 Reference Table: Combined Gas Law

This table shows how Pressure (P), Volume (V), and Temperature (T) change in different real-world scenarios.

ScenarioInitial (P₁, V₁, T₁)Final (P₂, V₂, T₂)Observation
Heating a sealed gas cylinderP₁=1 atm, V₁=10 L, T₁=300 KP₂=1.3 atm, V₂=10 L, T₂=390 KPressure increases with temperature at constant volume.
Inflating a balloon outdoorsP₁=1 atm, V₁=2 L, T₁=300 KP₂=1 atm, V₂=2.4 L, T₂=360 KVolume expands as temperature increases under constant pressure.
Scuba diver descending underwaterP₁=1 atm, V₁=6 L, T₁=298 KP₂=2 atm, V₂=3 L, T₂=298 KVolume decreases as external pressure increases at constant temperature.
Car tire on a hot dayP₁=2 atm, V₁=30 L, T₁=290 KP₂=2.2 atm, V₂=30 L, T₂=320 KPressure rises as the tire heats up at constant volume.

FAQs


Why do we use the Combined Gas Law?

We use it to calculate how a gas behaves when conditions like pressure, volume, or temperature change. It’s very useful in real-world situations like scuba diving, hot air balloons, or car tires heating up.

What happens if volume stays the same?

If volume stays constant, then pressure and temperature change proportionally. That is basically Gay-Lussac’s law.

What happens if temperature stays the same?

If the temperature is constant, the gas follows Boyle’s law — pressure increases when volume decreases, and vice versa.

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