How many moles of hydrogen gas would be needed to react with excess carbon dioxide to produce 53.6 moles of water vapor?

You first need to write your chemical equation:

CO2 + 4 H2 → CH4 + 2 H2O (balanced equation)

4 moles of hydrogen gas will produce 2 moles of water vapor since carbon dioxide is in excess.

ratio is then 4 H2 / 2 H2O

If you produce 30.6 moles of water vapor, how many moles of hydrogen gas is needed:
let's solve with ratio 4 H2 / 2 H2O = x H2 / 30.6 H2O

Therefore you need twice as many moles of hydrogen gas: 61.2 moles of hydrogen gas is needed.

Hope it helps.

The main types of electromagnetic radiation. radio  waves have  the lowest frequencies  and  longest  wavelengths, while gamma  waves have highest frequencies  and shortest wavelengths. the wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m.hope it !