Calculating Moles of Ammonia Gas

Oct 13, 2025 by wbrum.org 8 views

Introduction

In chemistry, understanding the number of moles of a substance is crucial for various calculations, including stoichiometry and chemical reactions. In this article, we will calculate the number of moles of ammonia gas ($$NH_3$$) in a given volume at standard temperature and pressure (STP).

Standard Temperature and Pressure (STP)

STP is defined as a temperature of $$0^\circ C$$ (or $$273.15 , \text{K}$$) and a pressure of $$1 , \text{atm}$$ (or $$101.325 , \text{kPa}$$). At STP, the volume of a gas is $$22.4 , \text{dm}^3$$ per mole.

Molar Volume of a Gas

The molar volume of a gas is the volume occupied by one mole of the gas at STP. For an ideal gas, the molar volume is constant and is equal to $$22.4 , \text{dm}^3$$ per mole.

Calculating Moles of Ammonia Gas

To calculate the number of moles of ammonia gas in a given volume, we can use the following formula:

n = \frac{V}{V_m}

where $$n$$ is the number of moles, $$V$$ is the given volume, and $$V_m$$ is the molar volume.

Given Values

Volume of ammonia gas: $$72 , \text{dm}^3$$
Molar volume of ammonia gas at STP: $$22.4 , \text{dm}^3$$ per mole

Calculations

Using the formula above, we can calculate the number of moles of ammonia gas as follows:

n = \frac{72 \, \text{dm}^3}{22.4 \, \text{dm}^3 \, \text{mol}^{-1}}

n = 3.21 \, \text{mol}

Conclusion

In this article, we calculated the number of moles of ammonia gas in a given volume at standard temperature and pressure (STP). We used the formula $$n = \frac{V}{V_m}$$ to calculate the number of moles, where $$n$$ is the number of moles, $$V$$ is the given volume, and $$V_m$$ is the molar volume. The result shows that the number of moles of ammonia gas in a volume of $$72 , \text{dm}^3$$ at STP is $$3.21 , \text{mol}$$.

References

International Union of Pure and Applied Chemistry (IUPAC). (2019). Standard Temperature and Pressure.
National Institute of Standards and Technology (NIST). (2022). Molar Volume of Gases.

Additional Information

The molar volume of a gas is a fundamental concept in chemistry and is used to calculate the number of moles of a gas in a given volume.
The standard temperature and pressure (STP) is a reference point for many chemical calculations and is defined as a temperature of $$0^\circ C$$ and a pressure of $$1 , \text{atm}$$.
The number of moles of a gas can be calculated using the formula $$n = \frac{V}{V_m}$$, where $$n$$ is the number of moles, $$V$$ is the given volume, and $$V_m$$ is the molar volume.
Calculating Moles of Ammonia Gas at Standard Temperature and Pressure: Q&A ====================================================================

Introduction

In our previous article, we calculated the number of moles of ammonia gas in a given volume at standard temperature and pressure (STP). In this article, we will answer some frequently asked questions related to calculating moles of a gas at STP.

Q: What is standard temperature and pressure (STP)?

A: STP is defined as a temperature of $$0^\circ C$$ (or $$273.15 , \text{K}$$) and a pressure of $$1 , \text{atm}$$ (or $$101.325 , \text{kPa}$$). At STP, the volume of a gas is $$22.4 , \text{dm}^3$$ per mole.

Q: What is the molar volume of a gas?

A: The molar volume of a gas is the volume occupied by one mole of the gas at STP. For an ideal gas, the molar volume is constant and is equal to $$22.4 , \text{dm}^3$$ per mole.

Q: How do I calculate the number of moles of a gas at STP?

A: To calculate the number of moles of a gas at STP, you can use the following formula:

n = \frac{V}{V_m}

where $$n$$ is the number of moles, $$V$$ is the given volume, and $$V_m$$ is the molar volume.

Q: What is the given volume in the formula?

A: The given volume is the volume of the gas that you want to calculate the number of moles for. For example, if you want to calculate the number of moles of ammonia gas in a volume of $$72 , \text{dm}^3$$, the given volume is $$72 , \text{dm}^3$$.

Q: What is the molar volume in the formula?

A: The molar volume is the volume occupied by one mole of the gas at STP. For an ideal gas, the molar volume is constant and is equal to $$22.4 , \text{dm}^3$$ per mole.

Q: Can I use the formula to calculate the number of moles of a gas at any temperature and pressure?

A: No, the formula is only applicable at standard temperature and pressure (STP). If you want to calculate the number of moles of a gas at a different temperature and pressure, you will need to use a different formula or consult a reference table.

Q: What is the unit of the number of moles?

A: The unit of the number of moles is moles (mol).

Q: Can I use the formula to calculate the number of moles of a gas in a volume that is not at STP?

A: No, the formula is only applicable at standard temperature and pressure (STP). If you want to calculate the number of moles of a gas in a volume that is not at STP, you will need to use a different formula or consult a reference table.

Conclusion

In this article, we answered some frequently asked questions related to calculating moles of a gas at standard temperature and pressure (STP). We hope that this article has been helpful in clarifying any confusion you may have had about calculating moles of a gas at STP.

References

International Union of Pure and Applied Chemistry (IUPAC). (2019). Standard Temperature and Pressure.
National Institute of Standards and Technology (NIST). (2022). Molar Volume of Gases.

Additional Information

The molar volume of a gas is a fundamental concept in chemistry and is used to calculate the number of moles of a gas in a given volume.
The standard temperature and pressure (STP) is a reference point for many chemical calculations and is defined as a temperature of $$0^\circ C$$ and a pressure of $$1 , \text{atm}$$.
The number of moles of a gas can be calculated using the formula $$n = \frac{V}{V_m}$$, where $$n$$ is the number of moles, $$V$$ is the given volume, and $$V_m$$ is the molar volume.