Converting Pressure to Atmospheres

Oct 13, 2025 by wbrum.org 89 views

Understanding the Problem

The problem requires us to find the volume of a gas at Standard Temperature and Pressure (STP) given its initial volume and pressure at a different temperature and pressure. To solve this problem, we need to use the ideal gas law, which relates the pressure, volume, and temperature of a gas.

The Ideal Gas Law

The ideal gas law is given by the equation:

PV = nRT

where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of the gas, R is the gas constant, and T is the temperature of the gas in Kelvin.

Converting Units

To solve this problem, we need to convert the given values to the appropriate units. The pressure is given in millimeters of mercury (mm Hg), which we need to convert to atmospheres (atm). The temperature is given in degrees Celsius (°C), which we need to convert to Kelvin (K).

1 atm = 760 mm Hg 0°C = 273.15 K

Given Values

Pressure (P1) = 800 mm Hg
Temperature (T1) = 30°C
Volume (V1) = 480 ml
Number of moles (n) = 1 (assuming a single mole of gas)

Converting Pressure to Atmospheres

P1 (atm) = 800 mm Hg / 760 mm Hg/atm = 1.053 atm

Converting Temperature to Kelvin

T1 (K) = 30°C + 273.15 K = 303.15 K

Using the Ideal Gas Law

We can now use the ideal gas law to find the volume of the gas at STP (1 atm, 0°C). We will assume that the number of moles of the gas remains constant.

P1V1/T1 = P2V2/T2

where P1 and V1 are the initial pressure and volume, T1 is the initial temperature, P2 and V2 are the final pressure and volume, and T2 is the final temperature.

Solving for V2

Rearranging the equation to solve for V2, we get:

V2 = P1V1T2 / P2T1

Substituting the given values, we get:

V2 = (1.053 atm)(480 ml)(273.15 K) / (1 atm)(303.15 K)

Calculating the Volume

V2 = 219.7 ml

Conclusion

The volume of the gas at STP is 219.7 ml.

Answer

The correct answer is C. 219.7 ml.

Discussion

This problem requires us to use the ideal gas law to find the volume of a gas at STP given its initial volume and pressure at a different temperature and pressure. We need to convert the given values to the appropriate units and use the ideal gas law to solve for the final volume. This problem is a good example of how to use the ideal gas law to solve problems involving gases.

Key Concepts

Ideal gas law
Converting units
Using the ideal gas law to solve problems involving gases

References

Chemistry textbook
Online resources

Additional Resources

Ideal gas law calculator
Online chemistry resources

Practice Problems

Find the volume of a gas at STP given its initial volume and pressure at 100°C and 2 atm.
Find the pressure of a gas at 30°C given its initial pressure and volume at 0°C and 1 atm.

Conclusion

Frequently Asked Questions

Q: What is the ideal gas law?

A: The ideal gas law is a mathematical equation that relates the pressure, volume, and temperature of a gas. It is given by the equation PV = nRT, where P is the pressure of the gas, V is the volume of the gas, n is the number of moles of the gas, R is the gas constant, and T is the temperature of the gas in Kelvin.

Q: What is STP?

A: STP stands for Standard Temperature and Pressure. It is a set of conditions that are used as a reference point for measuring the properties of gases. The conditions are 1 atm of pressure and 0°C (273.15 K) of temperature.

Q: How do I convert mm Hg to atm?

A: To convert mm Hg to atm, you can use the following conversion factor: 1 atm = 760 mm Hg. So, if you have a pressure in mm Hg, you can convert it to atm by dividing by 760.

Q: How do I convert °C to K?

A: To convert °C to K, you can add 273.15 to the temperature in °C. For example, if the temperature is 30°C, you can convert it to K by adding 273.15, which gives you 303.15 K.

Q: What is the gas constant (R)?

A: The gas constant (R) is a constant that is used in the ideal gas law. It is approximately equal to 0.0821 L atm/mol K.

Q: How do I use the ideal gas law to solve problems involving gases?

A: To use the ideal gas law to solve problems involving gases, you need to follow these steps:

Write down the given values and the unknown value.
Convert the given values to the appropriate units.
Use the ideal gas law to set up an equation that relates the given values and the unknown value.
Solve the equation for the unknown value.

Q: What are some common mistakes to avoid when using the ideal gas law?

A: Some common mistakes to avoid when using the ideal gas law include:

Not converting the given values to the appropriate units.
Not using the correct values for the gas constant (R) and the temperature in Kelvin.
Not solving the equation correctly.

Q: What are some real-world applications of the ideal gas law?

A: The ideal gas law has many real-world applications, including:

Calculating the volume of a gas at STP.
Calculating the pressure of a gas at a given temperature and volume.
Calculating the number of moles of a gas at a given pressure and temperature.

Q: How do I practice using the ideal gas law?

A: You can practice using the ideal gas law by working through problems and exercises that involve gases. You can also use online resources and calculators to help you solve problems and check your answers.

Conclusion

In conclusion, the ideal gas law is a powerful tool for calculating the properties of gases. By understanding the ideal gas law and how to use it, you can solve a wide range of problems involving gases. Remember to convert the given values to the appropriate units, use the correct values for the gas constant (R) and the temperature in Kelvin, and solve the equation correctly. With practice and experience, you will become proficient in using the ideal gas law to solve problems involving gases.