How many moles of water vapor react to yield 546.234 moles of hydrogen?

Answer 1

React with what to form what? I assume that is to decompose to H2 and O2 but I don't know that.
Write the equation.
2H2O ==> 2H2 + O2
546.234 mols H2 x (2 mol H2O/2 mol H2) = 546.234 x (2/2) = 546.234 x 1/1 = 546.234 mol H2O.
It's done with the coefficients.
2H2O