Calculations based on chemical equations - mass-mole calculation

Given the balanced chemical equation AND the mass of any one of the reactants or products, the moles of any other reactant or product can be determined by using the appropriate stoichiometric mole ratio of the reactants and products.

Example

How many moles of carbon dioxide gas is produced when 20.5 grams of ethyl alcohol, C₂H₅OH, is burned?

Step 1: Identify the chemical equation involved: a combustion reaction.

Step 2: Write the balanced chemical equation.

Step 2a: Convert the mass of C₂H₅OH to moles of C₂H₅OH.

Step 3: Determine the stoichiometric ratio of the substances that you are working with, specifically between CO₂ and C₂H₅OH.

Mole ratio of CO₂ : C₂H₅OH is 2:1.

Step 4: Calculate the number of moles of CO₂ by making the ratio specifically for the number of moles of C₂H₅OH from step 2a.

Content suitability

BCIT courses: CHEM 0011