combined gas law problems worksheet

3 min read 02-02-2025

This worksheet will guide you through solving combined gas law problems. The combined gas law is a crucial concept in chemistry, combining Boyle's, Charles's, and Gay-Lussac's laws to relate pressure, volume, and temperature of a gas under different conditions. Understanding and mastering this law is essential for any student of chemistry or related fields.

Before we dive into the problems, let's review the combined gas law formula:

(P₁V₁)/T₁ = (P₂V₂)/T₂

Where:

P₁ = Initial pressure
V₁ = Initial volume
T₁ = Initial temperature (in Kelvin!)
P₂ = Final pressure
V₂ = Final volume
T₂ = Final temperature (in Kelvin!)

Important Note: Always convert Celsius temperatures to Kelvin using the formula: K = °C + 273.15 Failure to do this will result in incorrect answers.

Types of Combined Gas Law Problems

Combined gas law problems can take various forms, but they all involve manipulating the formula above to solve for an unknown variable. Here are some common scenarios:

1. Finding a Missing Variable (P, V, or T):

These problems give you five of the six variables and ask you to calculate the sixth. This is the most straightforward application of the combined gas law.

Example: A gas occupies 5.0 L at 25°C and 1.0 atm. If the temperature is increased to 50°C and the pressure is increased to 2.0 atm, what will be the new volume?

2. Determining the Effect of Changes in Two Variables:

These problems involve assessing how changes in two variables (while holding the third constant or changing it proportionally) will affect the third. For example, how will doubling the pressure and halving the temperature affect the volume?

Example: A gas sample has a volume of 10 L at 27°C and 1 atm. If the pressure is doubled and the temperature is halved, what is the new volume?

3. Problems Involving Unit Conversions:

Some problems require you to convert units before applying the combined gas law. Pay close attention to the units of pressure (atm, kPa, mmHg), volume (L, mL), and temperature (K, °C).

Example: A gas occupies 200 mL at 20°C and 760 mmHg. What volume will it occupy at 100°C and 700 mmHg?

Worksheet Problems

Now let's put your knowledge to the test! Solve the following problems, showing your work clearly. Remember to convert temperatures to Kelvin and pay close attention to units.

Problem 1: A sample of gas has a volume of 2.5 L at 20°C and 1.5 atm. What will be its volume if the temperature is increased to 40°C and the pressure is decreased to 1.0 atm?

Problem 2: A balloon is filled with 3.0 L of helium at 25°C and 1.0 atm. If the balloon rises to an altitude where the pressure is 0.75 atm and the temperature is -10°C, what will be its new volume?

Problem 3: A gas occupies 100 mL at 27°C and 750 mmHg. What will its pressure be if the volume is reduced to 50 mL and the temperature is increased to 127°C?

Problem 4: A gas at 1.0 atm and 25°C occupies a volume of 20 L. If the pressure is increased to 2.5 atm while keeping the temperature constant, what happens to the volume?

Answer Key (Provided separately to encourage independent problem-solving)

This answer key will be provided separately to allow you to challenge yourself and fully grasp the concepts involved before checking your work. Contact me if you would like the answer key.

By working through these problems, you will solidify your understanding of the combined gas law and its applications. Remember to practice regularly and consult your textbook or teacher for further assistance if needed. Good luck!