Stoichiometric calculations relate the quantities and quantities of chemical elements.

The concept of mol is widely used in these calculations. It is very important to know how to turn the gram unit into mol. You can use the following formula:

Where:

n = mol number (amount of matter)

m = mass in grams

MM = molar mass (g / mol)

Example:

How many grams are in 2 mol of CO_{2}?

** **

This calculation can also be done by rule of three:

For calculations with a rule of three, we must always place the equal units one below the other, as in the example above.

See other examples of stoichiometric calculations involving only the chemical formula:

- How many moles are there in 90g H
_{2}O?

90 = 18. x

**5 mol = x**

- How many water molecules are there in 3 moles of H
_{2}O?

x = 3. 6.02.10^{23}**x = 18.06. 10 ^{23} or 1,806.10^{24} molecules**

- What is the volume occupied by 4 moles of gas Cl
_{2}on CNTP?

x = 4 x 22.4**x = 89.6L**

- 4) How many moles are there in 89.6L of CO gas
_{2}on CNTP?

**x = 4 mol **