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**Avogadro’s law formula**, expressed as V_{1}/n_{1} = V_{2}/n_{2}, relates the volume of a given quantity of gas to its number of moles. In this formula, V_{1} and n_{1} represent the initial volume and number of moles of the gas, while V_{2} and n_{2} represent the final volume and number of moles, respectively. This formula can be used to calculate the volume or number of moles of a gas under different conditions, given the initial volume and number of moles of the gas.

## Practice problems

### Problem #1

A rubber ball contains 5 L of gas with 0.4 moles of helium at a given temperature and pressure. Determine the final volume of the gas when an additional 2 moles of helium are added to the rubber ball.

**Solution**

Given data:

- Initial volume of the gas, V
_{1}= 5 L - Initial number of moles of the gas, n
_{1}= 0.4 mol - Final volume of the gas, V
_{2}= ? - Final number of moles of the gas, n
_{2}= 0.4 mol + 2 mol = 2.4 mol

Applying the formula:

- V
_{1}/n_{1}= V_{2}/n_{2} - V
_{2}= (V_{1}× n_{2}) ÷ n_{1} - V
_{2}= (5 × 2.4) ÷ 0.4 - V
_{2}= 12 ÷ 0.4 - V
_{2}= 30 L

Therefore, the final volume of the gas is **30 L**.

### Problem #2

A tube contains 6 L of gas with 0.8 moles of hydrogen gas at a certain temperature and pressure. Find the final number of moles of gas when the volume of the gas increases to 12 L.

**Solution**

Given data:

- Initial volume of the gas, V
_{1}= 6 L - Initial number of moles of the gas, n
_{1}= 0.8 mol - Final number of moles of the gas, n
_{2}= ? - Final volume of the gas, V
_{2}= 12 L

Applying the formula:

- V
_{1}/n_{1}= V_{2}/n_{2} - n
_{2}= (n_{1}× V_{2}) ÷ V_{1} - n
_{2}= (0.8 × 12) ÷ 6 - n
_{2}= 0.8 × 2 - n
_{2}= 1.6 mol

Therefore, the final number of moles of the gas is **1.6 mol**.

### Problem #3

A container is filled with a few liters of gas containing 0.7 moles of helium gas. If the volume of the gas is increased to 9 L and an additional 1.2 moles of argon gas are added to the container, then what was the initial volume of the gas?

**Solution**

Given data:

- Initial number of moles of the gas, n
_{1}= 0.7 mol - Final volume of the gas, V
_{2}= 9 L - Final number of moles of the gas, n
_{2}= 0.7 mol + 1.2 mol = 1.9 mol - Initial volume of the gas, V
_{1}= ?

Applying the formula:

- V
_{1}/n_{1}= V_{2}/n_{2} - V
_{1}= (V_{2}× n_{1}) ÷ n_{2} - V
_{1}= (9 × 0.7) ÷ 1.9 - V
_{1}= 6.3 ÷ 1.9 - V
_{1}= 3.31 L

Therefore, the initial volume of the gas is **3.31 L**.

### Problem #4

A balloon is initially filled with 3 L of gas containing some moles of argon gas. If the volume of the gas is increased to 9 L and an additional 3 moles of argon gas are added to the balloon, what was the initial number of moles of the gas?

**Solution**

Given data:

- Initial volume of the gas, V
_{1}= 3 L - Final volume of the gas, V
_{2}= 9 L - Final number of moles of the gas, n
_{2}= 3 mol - Initial number of moles of the gas, n
_{1}= ?

Applying the formula:

- V
_{1}/n_{1}= V_{2}/n_{2} - n
_{1}= (V_{1}× n_{2}) ÷ V_{2} - n
_{1}= (3 × 3) ÷ 9 - n
_{1}= 9 ÷ 9 - n
_{1}= 1 mol

Therefore, the initial number of moles of the gas is **1 mol**.

## Related

- Boyle’s law formula
- Charles law formula
- Gay-Lussac’s law formula
**Avogadro’s law formula**- Ideal gas law formula
- Dalton’s law formula
- Henry’s law equation
- Combined gas law formula

## External links

- Avogadro’s Law – Chemistry LibreTexts
- Avogadro’s law | Definition, Explanation, & Facts – Britannica
- Avogadro’s Law — Overview & Formula – Expii
- Avogadro’s Law Study Guide – Inspirit VR
- What is the formula for Avogadro’s law? – Homework.Study.com
- Gas Law – Avogadro’s Law – ChemTeam
- Avogadro’s law – Wikipedia
- Avogadro’s Law: Definition, Formula, Equation and Examples – Science ABC
- What is Avogadro’s Law? + Example – Socratic
- What Is Avogadro’s Law? Definition and Example – ThoughtCo
- Avogadro’s Law – Chemistry Steps
- Avogadro’s Law Calculator V1/n1=V2/n2 – SensorsONE
- Avogadro’s Law Made Easy | Understanding Gas Laws – ChemTalk
- Avogadro’s Law: Statement, Formula, Examples, and Problems – Chemistry Learner
- Avogadro’s Law – Definition, Formula, Examples – Science Notes and Projects
- Avogadro’s law Formula – SoftSchools.com
- Boyle’s Law, Charles’ Law, Avogadro’s Law Examples – Medium
- Avogadro’s Law: Derivation, Application, Limitation – The Chemistry Notes

Deep

Learnool.com was founded by Deep Rana, who is a mechanical engineer by profession and a blogger by passion. He has a good conceptual knowledge on different educational topics and he provides the same on this website. He loves to learn something new everyday and believes that the best utilization of free time is developing a new skill.