Example Of Avogadro's Law In Real Life

Avogadro’s law tells about the relationship between the volume of a gas and the number of molecules possessed by it. It was formulated by an Italian scientist Amedeo Avogadro in the year 1811. During a series of experiments conducted by him, he observed that an equal volume of gases contains an equal number of particles. In other words, Avogadro’s law states that for an ideal gas, the volume of the gas is directly proportional to the number of moles possessed by it provided a constant temperature and pressure is maintained. This means that with an increase in volume, the number of moles will increase. Similarly, with a decrease in volume, the number of moles will also decrease. It is also known as Avogadro’s principle or Avogadro’s hypothesis. It is only applicable to ideal gases and gives an approximate result for the real gases. The gases with light molecules such as helium, hydrogen, etc. obey Avogadro’s law in a better manner as compared to the gases with heavy molecules.


1. Breathing

Italian Scientist Amedeo Avogadro Source: Google. This law is an experimental gas law. Specifically, this law is for an ideal gas. This law is not applicable to real gases because they show some variations. Understand Avogadro’s Law Examples, Ballons. Avogadro’s law states that –.

Just because the volume is held constant, Gay Lussac law is also known as the law of constant volume. In this article, I will be giving you a brief analysis of Top 6 Real-Life Gay Lussac Law Examples. Well, if you want to know more about Gay Laussac’s law, you can check this article. I hope you will love it. Avogadro's law and Examples of Avogadro's law in Real Life Applications 1 of 3, 08:53 pm At the conditions of temperature and pressure, equal volumes. In fact, when Avogadro’s Law is substituted with Combined Gas Law (i.e the combination of Boyle’s Law, Charles’s Law, and Gay-Lussac’s Law) develops into an Ideal Gas Law. Moreover, Avogadro’s Law can be deduced from the Kinetic Molecular Theory Of Gas. Take a look at Top 6 Real-Life Gay Lussac Law Examples. General Consequences. Avogadro's Law applies to real life in many different ways. It explains why bread and baked goods rise. It explains gunpowder and projectiles.

Human lungs demonstrate Avogadro’s law in the best possible way. When we inhale, the lungs expand because they get filled with air. Similarly while exhaling, the lungs let the air out and shrink in size. The change in volume can be clearly observed, which is proportional to the amount or the number of molecules of air contained by the lungs.

2. Inflating Balloon

To inflate a balloon it is required to be stuffed up with air molecules that are blown inside it either through the mouth or with the help of a pump. If you decrease the amount of air contained by the balloon, a significant decrease in the volume or the size of the balloon can be observed. Hence, Avogadro’s law can be observed in action.

3. Filling Tyres with Air

Flat tyres do not contain a sufficient amount of air molecules in them, which is why they lack proper shape. When the flat tyre of a vehicle is attached to an air pump, the air molecules get pressed into it. The number of particles of air present in the flat tyre increase; therefore, the volume increases accordingly. This helps the tyre to regain its original shape. Hence, the inflation of flat tyres is a clear demonstration of Avogadro’s law in everyday life.

4. Pumping Air in a Ball

A sports ball contains a bladder and a rigid outer covering. When the ball gets deflated the bladder gets deprived of air and loses its shape. Thereby, causing the ball to lose the ability to bounce. The volume of the air present in the bladder can be increased by forcefully pressing air into it through an air pump. The change in volume of air is proportionate to the change in the number of air molecules possessed by it. Hence, pumping air in a sports ball is an explicit illustration of Avogadro’s law in real life.

5. Bicycle Pump Action

The action of a bicycle pump makes use of Avogadro’s law. The pump extracts the air from the environment and pushes it inside the structure of the deflated object. The increase in the number of gas molecules in the object correspondingly changes its shape and helps it to expand. This proportionality between the number of molecules of the air and the volume is nothing but Avogadro’s law.

6. Pool Tube

The pool tube, in deflated form, is easily portable in nature. The absence or scarcity of the number of molecules in the tube reduces the volume and makes it compact. During inflation, when the tube is filled with air, the number of air molecules inside it increases. Thereby, increasing the volume and size of the pool tube. Hence, Avogadro’s law can be implemented to inflate or deflate the pool tube as per the requirement.

05th Apr 2019 @ 11 min read

Avogadro's law is also known as Avogadro's hypothesis or Avogadro's principle. The law dictates the relationship between the volume of a gas to the number of molecules the gas possesses. This law like Boyle's law, Charles's law, and Gay-Lussac's law is a specific case of the ideal gas law. This law is named after Italian scientist Amedeo Avogadro. He formulated this relationship in 1811. After conducting the experiments, Avogadro hypothesized that the equal volumes of gas contain the equal number of particles. The hypothesis also reconciled Dalton atomic theory. In 1814 French Physicist Andre-Marie Ampere published similar results. Hence, the law is also known as Avogadro-Ampere hypothesis.


For an ideal gas, equal volumes of the gas contain the equal number of molecules (or moles) at a constant temperature and pressure.

In other words, for an ideal gas, the volume is directly proportional to its amount (moles) at a constant temperature and pressure.


As the law states: volume and the amount of gas (moles) are directly proportional to each other at constant volume and pressure. The statement can mathematically express as:

Replacing the proportionality,

where k is a constant of proportionality.

The above expression can be rearranged as:

The above expression is valid for constant pressure and temperature. From Avogadro's law, with an increase in the volume of a gas, the number of moles of the gas also increases and as the volume decreases, the number of moles also decreases.

If V1, V2 and n1, n2 are the volumes and moles of a gas at condition 1 and condition 2 at constant temperature and pressure, then using Avogadro's law we can formulate the equation below.

Let the volume V2 at condition 2 be twice the volume V1 at condition 1.

Therefore, with doubling the volume, the number of moles also gets double.

The formation of water from hydrogen and oxygen is as follows:

$underset{1,text{mol}}{ce{H2O}}$}' alt='Water reaction'>

In the above reaction, 1 mol, (nH2) of hydrogen gas reacts with a 12 mol (nO2) of oxygen gas to form 1 mol (nH2O) of water vapour. The consumption of hydrogen is twice the consumption of oxygen which is expressed below as:

Let say, 1 mol of hydrogen occupies volume VH2, a 12 mol of oxygen occupies VO2 and similarly for 1 mol of water vapour, volume VH2O. As we know from Avogadro's law, equal volumes contain equal moles. Hence, the relationship between the volumes is the same as among the moles as follows:

Avogadro's law along with Boyles' law, Charles's law and Gay-Lussac's forms ideal gas law.

Graphical Representation

The graphical representation of Avogadro's law is shown below.

The above graph is plotted at constant temperature and pressure. As we can observe from the graph that the volume and mole have a linear relationship with the line of a positive slope passing through the origin.

As shown in the above figure, the line is parallel to the x-axis. It means that the value of volume by mole is constant and is not influenced by any change in mole (or volume).

Both the above graphs are plotted at a constant temperature and pressure.

Avogadro's constant

The Avogadro's constant is a constant named after Avogadro, but Avogadro did not discover it. The Avogadro's constant is a very useful number; the number defines the number of particles constitutes in any material. It is denoted by NA and has dimension mol−1. Its approximate value is given below.

Molar Volume

Since Avogadro's law deals with the volume and moles of a gas, it is necessary to discuss the concept of molar volume. The molar volume as from the name itself is defined as volume per mole. It is denoted as Vm and having a unit of volume divided by a unit of mole (e.g. dm3 mol−1, m3 kmol−1, cm3 mol−1 etc). From the ideal gas law, at STP (T = 273.15 K, P = 101 325 Pa) the molar volume is calculated as:

Limitation of Avogadro's law

The limitation are as follows:

  • The law works perfectly only for ideal gases.
  • The law is approximate for real gases at low pressure and/or high temperature.
  • At low temperature and/or high pressure, the ratio of volume to mole is slightly more for real gases compare to ideal gases. This is because of the expansion of real gases due to intermolecular repulsion forces at high pressure.
  • Lighter gas molecules like hydrogen, helium etc., obey Avogadro's law better in comparison to heavy molecules.

Real World Applications of Avogadro's Law

Avogadro's principle is easily observed in everyday life. Below are some of the mentioned.


When you blow up a balloon, you are literally forcing the air from your mouth to inside the balloon. In other words, you are filling more moles of air in the balloon and it expands.


Have you ever filled deflated tyres? If yes, then you are nothing but following Avogadro's law. When you pump air inside the deflated tyres at a gas station, the amount (moles) of gas inside the tyres is increased which increases the volume and the tyres are inflated.

Human lungs

When we inhale, air flows inside our lungs and they expand while when we exhale, the air flow from the lungs to surroundings and the lungs shrink.

Laboratory Experiment to prove Avogadro's law



To verify Avogadro's law by estimating the amount (moles) of different gases at a fixed volume, temperature and pressure.


The apparatus requires for this experiment is shown in the above diagram. It consists of a U-tube manometer (in the diagram closed-end manometer is used, but opened-end manometer can also be used) as depicted in the figure, mercury, a bulb, a vacuum pump, four to five cylinders of different gases and a thermometer. Connect the all apparatuses as shown in the figure.


  1. V0 is the volume of the bulb, which is known (or determined) before the experiment.
  2. T is the temperature at which the experiment is performed, which can be determined from the thermometer (for simplicity take it as room temperature).
  3. P is the pressure at which the experiment is performed, which can be determined from the difference in heights of mercury level in the manometer.
  4. W0 is the empty weight of the bulb, and it is known (or determined) before the experiment.
  5. W is the filled weight of the bulb.
  6. Wg is the weight of the gas inside the bulb.
  7. M is the molar mass of the gas.


  1. Take a gas cylinder attached it the bulb setup and also attached the pump to the bulb setup. Care must be taken while attaching the apparatus to prevent any leakages of the gas.
  2. First, close the knob of the gas cylinder and open the vacuum pump knob on the bulb. Evacuate the air filled in the system and by turning on the vacuum pump.
  3. Once the bulb is emptied, close the vacuum pump knob and switch off the vacuum pump.
  4. Start filling the bulb with the cylinder gas by opening the gas cylinder knob slowly until the desired difference in the mercury height is achieved. Note the height difference in the manometer. (The value of the height difference should be the same for all the readings.)
  5. Close all the knobs, also close the connection between the bulb and the manometer to isolate the gas inside the bulb. Disassemble the bulb from the manometer.
  6. Weigh the bulb on a weighing machine and note the reading down.
  7. This finishes the procedure for the first gas. Repeat the same procedure for different gases.


Calculate the weight of gas (Wg) in the bulb by subtracting the weight of empty bulb (W0) from the weight of the filled bulb (W).

Then calculate the number of moles of the gas as:

The number of moles of all gases should be approximately equal within a small percentage of error. If this is true, then all the gases do obey the Avogadro's law.

If the experiment is performed at STP (T = 273.15 K, P = 101 325 Pa) , then we can also calculate the molar volume Vm as:

And its value should be close to 22.4 dm3 mol−1.


Example 1

Example Of Avogadro

Consider 20 mol of hydrogen gas at temperature 0 °C and pressure 1 atm having the volume of 44.8 dm3. Calculate the volume of 50 mol of nitrogen gas, at the same temperature and pressure?

As from Avogadro's law at constant temperature and pressure,

Therefore, the volume is 112 dm3.

Example 2

There is the addition of 2.5 L of helium gas in 5.0 L of helium balloon; the balloon expands such that pressure and temperature remain constant. Estimate the final moles of gas if the gas initially possesses 8.0 mol.

Example Of Avogadro's Law In Real Life

The final volume is the addition of the initial volume and the volume added.

From Avogadro's law,

Celtic fc 1920 kitsempty spaces the blog. The final number of moles in 7.5 L of the gas is 12 mol.

Example 3

3.0 L of hydrogen reacts with oxygen to produce water vapour. Calculate the volume of oxygen consumed during the reaction (assume Avogadro's law holds)?

For the consumption of every one mole of hydrogen gas, half a mole of oxygen is consumed.

Example Of Avogadro's Law In Real Lifee

As per Avogadro's law, the volume is directly proportional to moles, so we can rewrite the above equation as:

1.5 L of oxygen is consumed during the reaction.

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