Chemistry Stoichiometry

Question

If 200.8 g of carbon dioxide gas is made from the complete combustion of isopropanol (C3H7OH), how many moles of oxygen are used up?

Answer 1

Step 1 - determine the chemical equation for the word problem.

combustion is the addition of oxygen to form CO2 and H2O - in regards to hydrocarbons.

C₃H₇OH + O₂ -----> CO₂ + H2O

Next, balance the chemical equation

2C₃H₇OH + 9O₂ -----> 6CO₂ + 8H2O

The word problem asks us to convert grams of CO2 to moles of O2.

We will need to find molar mass of CO2 = 12 + 2(16) = 44 g/mol

200.8 g CO2 x 1 mole CO2 x 9 mol O2 = 200.8/44*9/6 = 6.85 mol O2

44 g CO2 6 mol CO2