Molar Mass?
The first step of finding the limiting reagent is calculating the molar mass of each chemical compound. Example:
2CH2Cl2+3O2=>2CO2+2H2O+2Cl2
For the balanced equation shown above, what would be the limiting reagent if 76.0 grams of CH2Cl2 were reacted with 69.8 grams of O2?
We need to find the molar mass. We do this by looking at the atomic number of each element in the compound:
C = 12
H = 1
Cl = 35.5
O = 16
Then we multiply there atomic number by how many atoms there are of this element in the compound:
12 x 1 = 12
1 x 2 = 2
35.5 x 2 = 70
16 x 2 = 32
Finally we add these calculations together:
12+2+70 = 84 grams/mole
16 = 16 grams/mole
And there you go, you now know how to calculate molar mass.