At STP, a sample of methane gas (CH4) is combusted to produce 1.2 L carbon dioxide. What volume of oxygen was required for the reaction to occur?

Answer 1

Hey John,

Here are some steps that should help:

1) Write the balanced reaction. Remember that the combustion of hydrocarbons produces carbon dioxide and water. You should be able to check your answer to this with google.

2) Find out how many moles of carbon dioxide are contained in 1.2L at STP. Knowing that this is at STP is critical here. At STP, 1 mole of ANY gas takes up 22.4L of volume. So use that conversion to determine moles of CO₂.

3) Use the molar ratios (established in step 1) to determine how many moles of oxygen correspond to that many moles of carbon dioxide.

4) Again, use the STP relationship of 1 mol = 22.4 L. This will get you the volume of oxygen.