What is the law of ideal gas?

This may seem like a large volume, but it’s not. It’s almost half a liter, so it’s half a bottle of soda.

Moles and particles

These moles are not hairy creatures that make holes in the ground. The name comes from molecules (which is obviously too long to write).

Here is an example to help you understand the idea of ​​a mole. Suppose you run an electric current through water. The water molecule is made up of one oxygen atom and two hydrogen atoms. (This is X2A.) This electric current decomposes the water molecule and produces hydrogen gas (H2) and oxygen gas (O2).

This is actually a fairly simple experiment. See it here:

Because water has twice as many hydrogen atoms as oxygen, you get twice as many hydrogen molecules. We can see this if we collect the gases from this water: We know the ratio of molecules, but we don’t know the number. That’s why we use moles. Basically, it’s just a way to count the countless.

Don’t worry, there really is a way to find the number of particles in a mole, but you need to Avogadro’s number for that. If you have one liter of air at room temperature and normal pressure (we call this atmospheric pressure), then there will be about 0.04 moles. (This would be n in the law of ideal gas.) Using Avogadro’s number, we get 2.4 x 1022 particles. You can’t count so high. Nobody can. But this is N, the number of particles, in the other version of the law of ideal gas.


Just a quick note: You almost always need some constant for an equation with variables representing different things. Just look at the right side of the ideal gas law, where we have pressure multiplied by volume. The units for this left side would be Newton-meters, which is the same as Joule, the unit of energy.

On the right is the number of moles and the temperature in Kelvin – these two obviously do not multiply to give joules. Notes must have the same units on both sides of the equation, otherwise it would be like comparing apples and oranges. Here comes the constant R. It has joule units / (mol × Kelvin), so mol × Kelvin is canceled and you just get joules. Boom: Now both sides have the same units.

Now let’s look at some examples of the ideal gas law using a simple rubber balloon.

Inflating a balloon

What happens when you blow a balloon? You are obviously adding air to the system. As you do this, the bubble becomes larger, so its volume increases.

How about the temperature and pressure inside? Let’s assume they are permanent.

I will include arrows next to the variables that are changing. The up arrow means increase and the down arrow means decrease.

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