Question

Given the reaction: H2 + O2 = HOH How many grams of hydrogen gas are needed to produce 11.2 moles of water vapor?

Answer 1

Answer: 22.6g H2

Step-by-step explanation:

You need to set up dimensional analysis starting with 11.2moles of H2O (the same as HOH).

First, you need to balance the equation. When balanced, it is:

2H2(g) + O2(g) --> 2H2O(g)

Starting with moles of H2O, you need to go from moles of H2O to moles of H2. To do so, you need to use the mole ratio that you can figure out from the balanced equation. In this case it will be 2mol H2/2mol H2O.

Then just convert to grams using the molar mass of H2 which is 2.016grams.

11.2 mol H2O x (2 mol H2 / 2 mol H2O) x (2.016g H2 / 1 mol H2) = 22.6g H2

When that equation is set up, all units except for grams of H2 will cancel and you'll be able to multiply across.