HS Chemistry - Working With Chemical Reactions

Calculating Amount of Products Produced

Overview of The Page

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Calculating amount of products produced given the mass of the reactants.

When we know the mass in grams we have of each of the reactants, we can calculate the amount of moles of reactants present. This allows us to calculate the amount, in moles, of products produced, which allows us to calculate the mass of the products produced in the chemical reaction.

Convert the mass $in grams$ to moles of substance, for each product, by dividing the mass we have by the mass of one mole of that reactant.
Find the amount, in moles, of product created. Take note of whichever reactant is least available $in terms of how many moles there are of that reactant$ - that's how much product is produced in moles.
Convert the number of moles of product to mass in grams.

Converting Mass to Moles

As an example, let's say we have 100 grams of Sodium Sulfate $Na~2~SO~4~$ , and we want to know how many moles of Sodium Sulfate we have.

First we need to find the mass of 1 formula unit of Na₂SO₄:

The mass of the 2 Sodium atoms is 45.98 amu

2 Na atoms 22.99 amu Na

2 × 22.99 = 45.98 amu Na 1 Na atom

The mass of the Sulfur atom is 32.07 amu

1 S atom 32.07 amu S

1 × 32.07 = 32.07 amu S 1 S atom

The mass of the 4 Oxygen atoms is 64.00 amu

4 O atoms 16.00 amu O

4 × 16.00 = 64.00 amu O 1 O atom

The mass of 1 formula unit of Na₂SO₄ is 45.98 + 32.07 + 64.00 = 142.05 amu

Therefore, the mass of 1 mole of Na₂SO₄ is 142.05 grams

Now we can divide the mass of our quantity of Na₂SO₄ $100 grams$ by the mass of 1 mole of Na₂SO₄ $142.05 grams$

100 grams / 142.05 grams ≈ 0.70

100 grams of Na₂SO₄ is 0.70 mol Na₂SO₄. We have 0.70 mol Na₂SO₄

Practice

You have 500 grams of calcium carbonate $CaCO~3~$ . How many moles of calcium carbonate do you have? Enter your answer below as a number rounded to three significant figures: