Mass-mole/mole-mass Stoich

In these type of problems we are either starting with chemicals in grams or we need to end in chemicals in grams.

How many grams of water can be made from ⅔ of a mole of O₂?

We are using the same steps here except adding one more. We need to convert the final moles into grams.

Steps to mole-mass or mass-mole problems:

1. Identify what information we are given and what we need to find.

given: ⅔ of a mole of O₂ , find: grams of water

2. Create a conversion factor from the balanced equation.

We need 2 oxygen for each 2 water.

2O₂/2H₂O or (reduced) O₂/H₂O

3. Multiply the given by the conversion factor.

⅔ O₂ x H₂O/O₂ = ⅔ H₂O *

*Notice that the oxygen needs to be in the denominator to cancel out the oxygen in the numerator.

4. Convert moles to mass by multiplying by the molar mass.

⅔ H₂O x 16.00 g/mol = 10.667g H₂O