Stoichiometry help?

Question

(a) If 5.90 mol of ethane, C2H6, undergo combustion according to the unbalanced equation given below, how many moles of oxygen are required?

C2H6 + O2 —> CO2 + H2O

_ mol

(b) How many moles of each product are formed?

CO2

_ mol

H2O

_ mol

Answer 1

So, first, you must balance the equation before you can proceed answering the question:

2C₂H₆ + 7O₂ ==> 4CO₂ + 6H₂O ... balanced equation

Now you can use dimensional analysis to find moles of O₂ required to react with 5.90 mols of 2C₂H₆:

5.90 mols 2C₂H₆ x 7 mols O₂ / 2 mols 2C₂H₆ = 20.7 mols O2 (to 3 sig. figs.)

To find moles of each product (CO₂ and H₂O), again use dimensional analysis:

5.90 mols 2C₂H₆ x 4 mols CO₂ / 2 mols 2C₂H₆ = 11.8 mols CO₂ (to 3 sig. figs.)

5.90 mols 2C₂H₆ x 6 mols H₂O / 2 mols 2C₂H₆ = 17.7 mols H₂O (to 3 sig. figs.)