First off, molarity is just a way of expressing the concentration of a solution. The molarity is the number of moles per liter of solution. A mole is defined as 6.022 x 1023 (also called Avogadro’s constant) molecules—that’s basically a six with 23 numbers behind it!

Secondly, every element or molecule has a molecular weight, or a mass per molecule of that compound.

For example, sodium chloride—NaCl—has a molecular weight of 58.443 grams per mole. This is, conveniently, also the number of grams per mole of this compound. Therefore, one mole of sodium chloride will weigh 58.443 grams.

Finally, if you know how much of your sodium chloride is in the solution, and you know how much liquid it is dissolved in, you can find the molar concentration.

Here’s an example:

You have 26 grams of NaCl dissolved in 0.6 liters of water. What is the molarity?

We know that NaCl is 58.443 grams per mole, and that we have 0.6 liters of water. We need to find

how many moles of NaCl there are per liter of water to get the molarity. Here is how we set the problem

up:

Secondly, every element or molecule has a molecular weight, or a mass per molecule of that compound.

For example, sodium chloride—NaCl—has a molecular weight of 58.443 grams per mole. This is, conveniently, also the number of grams per mole of this compound. Therefore, one mole of sodium chloride will weigh 58.443 grams.

Finally, if you know how much of your sodium chloride is in the solution, and you know how much liquid it is dissolved in, you can find the molar concentration.

Here’s an example:

You have 26 grams of NaCl dissolved in 0.6 liters of water. What is the molarity?

We know that NaCl is 58.443 grams per mole, and that we have 0.6 liters of water. We need to find

how many moles of NaCl there are per liter of water to get the molarity. Here is how we set the problem

up:

So the final answer is 0.742 molar (M) NaCl.