Talk:Units of Measurement

You didn't make moles easy to understand

Making Moles Easy to Understand:

Moles can be a very confusing part of chemistry for some people. But in reality moles are very easy to understand.

A Mole (abbreviated Mol) represents how many (atoms or molecules) there is of whatever substance is being measured - this number is compared to a base amount known as Agrovado's Constant.

Where moles become confusing for most people is when using them to determine weight. The number of grams in one mole varies from substance to substance, but put very simply, the molar mass of a substance is equivalent to its molecular weight in grams. Now, a single atom of Hydrogen is not the same weight as a single atom of Oxygen; think of it like this: one dozen eggs do not weigh the same as one dozen cars. Therefore, their molar mass will be different. Oxygen has a molecular weight of about 16, while Hydrogen has a molecular weight of about 1. You can find this on just about any periodic table. Their molecular weight in grams would be equivalent to their molar mass, so 1 mole of Hydrogen is 1 gram, and 1 mole of Oxygen is 16.

You can then extend this concept to determining the weight of one mole of any chemical compound. One mole of a chemical compound is equal to the molecular weight of that compound. You determine the molecular weight of a compound by adding the atomic weight of each element in the compound. Using water as an example: to determine the molecular weight of water, H2O, you add the atomic weight of oxygen (the atomic weight of oxygen is about 16) to the atomic weight both hydrogen atoms (the atomic weight of hydrogen is about 1). The weight of one oxygen and two hydrogen is roughly 18.0, the approximate molecular weight of water. So one mole of water is equal to approximately 18.0 grams.

More commonly used is the "Molar" or Mole per Liter, which utilizes the same sort of mathematics as the standard Mole. If a Formulation called for 0.5 molars (moles per liter) of Ammonium Nitrate, follow these steps:

1.) Determine the chemical formulation of the compound in question. Ammonium Nitrate is KNO3.

2.) Find the Molecular weight of the compound. The weight of K is 39, N is 14 and O is 16. 16+16+16+14+39 = 101.

3.) Convert to grams. 101 grams.

4.) Multiply by number of moles required. 0.5 moles means I multiply by a half, or divide by 2. 101 / 2 = 50.5

5.) Compare this amount against 1000/ml (one liter)

That's it! 0.5 molars of KNO3 is 50.5g/1000mL.

Uh-oh! It gets trickier. You're only making 250 mL - how much do you add?

Well, 250 is one quarter of 1000, so 250mL = 1000mL / 4. Therefore, we divide 50.5 by 4, and...

Approximately 12.6 grams per 250mL

By using moles you can calculate the number of molecules in a sample by weighing it. When you have one mole, you have 6.02 × 1023 molecules. . This number of molecules is known as Avogadro's Number or Avogadro's Constant.

etc etc