Question

Tungsten metal can be produced by the reaction of tungsten oxide powder (WO3) with hydrogen gas (H2) in a reactor heated to 800oC. The by-product of the reaction is water vapor (H2O). The reactor is charged with 128.0 kg of WO3 and 41.0 kg of H2. Assume that the reaction goes to completion.
Enter the number of kg of WO3 remaining:

Answer 1

This is a limiting reagent problem. Here is a post I've done explaining the steps for limiting reagent problems. Just follow the steps.
http://www.jiskha.com/science/chemistry/limiting_reagent_problem.html