Calculate the moles of oxygen needed to produce 0.090 mol of water. Be sure your answer has a unit symbol, if necessary, and round it to the correct number of significant digits.

Question

A major component of gasoline is octane CgH,8. When liquid octane is burned in air it reacts with oxygen (2) gas to produce carbon dioxide gas and water vapor.

Answer 1

You have a typo in your problem Octane is C₈H₁₈

Write an unbalanced chemical reaction equation that matches the word problem:

C₈H₁₈ + O₂ → CO₂ + H₂O

Balance the equation:

2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

In looking at the balanced chemical reaction equation, we see that it takes 25 moles of oxygen (O₂) to produce 18 moles of water therefore:

Round to 2 sig figs because 2 were given to start with therefore 0.13 moles of O₂ were required