If 26.4 moles of CH4 are reacted, how many moles of CO2 will be produced?

Answer 1

This question provides an amount of one substance reacted and asked for the amount of another substance produced, referring to a chemical reaction. You need the balanced chemical equation to answer it.

1. The combustion of CH₄ is written as: CH₄ + O₂ --> CO₂ + H₂O (This should have been given; you wouldn't normally be expected to know this from the top of your head)
2. Balancing by adding coefficients gives us: CH₄ + 2O₂ --> CO₂ + 2H₂O (and where there are no coefficients, we assume an invisible "1" coefficient)

The rest of the question requires us to use ratios. The most common/professional way to do this is to use unit analysis, aka the factor-label method, and multiply your given (26.4 moles CH₄) by the ratio between CO₂ and CH₄:

26.4 moles CH₄ x (1 mole CO₂ / 1 mole CH₄) = 26.4 moles CO₂

Since the ratio is 1:1, the number does not change. However if you were asked for moles of H₂O, it would be something like

26.4 moles CH₄ x (2 moles H₂O / 1 mole CH₄) = 52.8 moles H₂O

You can also solve problems like these by setting up a ratio equivalence, with the numbers from the question on one side and the coefficients on the other:

26.4 moles CH₄ = 1 mole CH₄

?? moles CO₂ 1 mole CO₂

Then you can solve using cross multiplication. This is a little easier for beginners to understand but once you get into multi-step problems, it's a bit clunky. I recommend getting used to unit analysis to make your Chemistry journey easier in the long run!