Alright, imagine you were making Kool-Aid, a popular drink. You need to add the right amount of sugar and Kool-Aid to the water. If you add too much, the resulting drink will be too strong (like the kool-Aid man); if you add too little, the resulting drink will be too weak. If you add the perfect amount, it will taste great. That Kool-Aid drink you made is a solution. A solution is a combination of a salute, the solid stuff your making (the Kool-Aid), and the solvent, the liquid used for dissolving (the water).

The main used solvent is just plain water, although there are other solvents out there like oil, and certain acids. Solvents can be anything that can be dissolved, in this case, Kool-Aid and sugar. More will be discussed in the next section

In chemistry, you and your teacher should perform certain reactions with chemicals dissolved in water. These chemicals, like the Kool-Aid, will have differing concentrations. These concentrations are measured using a special scale called molarity.

Molarity (or M) is basically moles per liter. Just think of it as how many moles of this substance will be dissolved if you had one liter of the solution.

Here�s the formula:

For example, if you made a solution by dissolving .311 moles of NaCl into 55 mL of water, what would be the molarity of the solution?

(don�t forget to make sure your dividing by liters not milliliters)

You can also use that formula to solve for other things:

You have a solution Al(NO₃)₃ of in a bottle. The label says that there�s 500 mL (.50 L) of the solution, and that the molarity of the solution is 3.21 M. calculate how many moles of Al(NO₃)₃ is in this solution.

1. Well, first change the equation so that it solves for moles:

moles (mol)	=	molarity (M)
liters (L)

liters(L)	x	moles (mol)	=	molarity (M) x liters (L)
		liters (L)

moles(mol) = molarity(M) x liters(L)

2. Then solve for moles:

3.21 M x .50 L = 1.6 moles of Al(NO₃)₃

• Just think of molarity as how many moles are in a liter of that solution (e.g. - .234 M means theres .234 moles in one liter of that solution).
• Remember to use liters when calculating molarity, even if all the problem gives you is the amount in milliliters.
• Remember to use sig figs in your calculations.
• Also, remember to make sure you use moles, do not use grams!