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Chemistry Units! Constants! Symbols! Formulas! Math Home Page! Formulas!

And now we turn to some examples of FORMULAS in Chemistry. Formulas are ways to come up with the answer you want. If you want to know the number of atoms in a solution, there is a formula. If you want to know the pressure of a gas in a tube, there is a formula. We have a couple here to get you started.

Gas Laws

So what you've got here is the Universal Gas Law. If you have a gas inside of a container, multiply the Pressure and the Volume and then divide by the Temperature, You will get a CONSTANT. The formula on the bottom is just moved around a little, but it says the same thing. If you know the Pressure, Volume and Temperature of a system, and you change something in the system, the answer will be the same (only if one of the other values change).

Confused? So think about this. (1) You have a system. (2) Multiply the Pressure and Volume. (3) Divide by the Temperature. The answer is 5. Now you go and change the Temperature. Since you know the answer still has to be "5", one or both of the other numbers (Pressure or Volume) has to change. If the system stays in the same container (that means the Volume is constant). Pressure will be the value that changes. If the value of "T" goes up, then the value of "P" must also goes up.

Gas Example
So if you solve the formula for the answer in the box you will come up with "10". The Pressure doubled when you doubled the Temperature.



Now you're sitting there with a solution in front of you. Your teacher walks up and asks you to figure out the MOLARITY of the solution. You used to look back with a blank look on your face. Now, thanks to CHEM4KIDS, you can use a formula to come up with the answer!

To figure out the Molarity you need two values. (1) The number of moles of substance that were put into the solution. And (2) the number of Liters of solution you have. You look at some salt water. You started with 10 moles of NaCl (Salt) and poured it into 1 Liter of Water (H2O). The Molarity is equal to 10 (10 divided by 1). Scientists would write 10M.

When you use symbols to show the formula you write it as M=n/V. Molarity equals the number of moles divided by the volume of solution in Liters.

Amedeo AvogadroThe famous Italian Chemist, Amedeo Avogadro, came up with an idea that if you have two volumes of gas, where both the temperature and pressure are the same, then they have the same number of molecules. And because he came up with it, chemists named it Avogadro's Law. Even though he was right, it wasn't until the 1850's that all the other scientists accepted the idea. It took nearly 40 years! And...

He was one of the first people to use the word "MOLECULE". As always, green hair was all the rage in Italy.

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