What Is the Ideal Gas Law?

This seems like a big volume, but it’s not. It’s almost half a liter, so that’s half a bottle of soda.

Moles and Particles

These moles are not furry creatures burrowing in the ground. The name comes from the molecule (which is obviously too long to write).

Here is an example to help you understand the concept of moles. Suppose you run an electric current through water. A water molecule consists of one oxygen atom and two hydrogen atoms. (this is H₂O.) This current splits water molecules to obtain hydrogen (H₂) and oxygen (O₂).

This is actually a very simple experiment. Check it out here:

Since water has twice as many hydrogen atoms as oxygen, you get twice as many hydrogen molecules. If we collect gas from water, we can see this: we know the proportion of molecules, but we don’t know the quantity. That’s why we use moles. It’s basically just a way to count the uncountable.

Don’t worry, there is indeed a way to find the number of particles in a mole – but you’ll need Avogadro’s number. If there is one liter of air at room temperature and atmospheric pressure (which we call atmospheric pressure), that’s about 0.04 moles. (This would be n in the ideal gas law.) Using the Avogadro number, we get 2.4 x 10^{twenty two} particle. You can’t count so high. No one can. But this is the number N of particles in another version of the ideal gas law.

constant

Just a quick note: For equations with variables representing different things, you almost always need some kind of constant. Looking at the right side of the ideal gas law, we have pressure times volume. The unit on the left is the Newton meter, which is the same as the unit of energy, the Joule.

On the right are the number of moles and the temperature in Kelvin – the two obviously cannot be multiplied to give the Joule unit.but you must The units on both sides of the equation are the same, otherwise it’s like comparing apples and oranges. This is where the constant R comes into play. It has units of joules/(mol × Kelvin), so mol × Kelvin cancels out and all you get is joules. Boom: Now both sides have the same units.

Now let’s look at some examples of the ideal gas law using ordinary rubber balloons.

inflate the balloon

What happens when you blow up a balloon? You are obviously adding air to the system. As you do this, the balloon will get bigger, so its volume will increase.

How is the temperature and pressure inside? Let’s assume they are constant.

I will add arrows next to the variable that changes. Up arrow means increase, down arrow means decrease.