If 32.9 grams of carbon monoxide and 18.8 grams of oxygen combine to form carbon dioxide, how many grams of carbon dioxide must form?

Question

Under certain conditions, the substances carbon monoxide and oxygen combine to form carbon dioxide.

If 32.9 grams of carbon monoxide and 18.8 grams of oxygen combine to form carbon dioxide, how many grams of carbon dioxide must form?

Answer 1

Answer 2

One way to do this is to first write the correctly balanced equation.

2CO + O₂ ==> 2CO₂

Then, you convert mass of CO and mass of O₂ to moles, determine which reactant is limiting, and find the mass of CO₂ formed.

CO: 32.9 g CO x 1 mol/28 g = 1.175 moles CO

O₂: 18.8 g O₂ x 1 mol/32 g = 0.5875 moles O₂

Since the mole ratio of CO to O₂ is 2:1 and there are twice as many moles of CO as O₂, neither is limiting.

Now, the moke ratio of CO to CO₂ is 1:1, 1.175 moles of CO₂ will be formed. The mass of CO₂will be

1.175 moles CO₂ x 44 g/mole = 51.7 g

You could also arrive at this same answer by simply adding the mass of CO to the mass of O₂ because of the law of conservation of matter and the fact that neither reactant is limiting.