Determine the moles of oxygen gas (O2) needed to completely react with 1.975 moles of hydrogen gas (H2). Final answers should be reported with the correct number of significant digits. H2 (g) + O2 (g) ⟶ H2O (g)

0.9875 moles of O₂

Explanation:

The reaction for production of water is:

2H₂ + O₂ → 2H₂O

By stoichiometry, 2 moles of hydrogen need 1 mol of oxygen to react.

Then, we can make the following rule of three:

If 2 moles of H₂ need 1 mol of O₂ to react

Then, 1.975 moles of H₂ will need ( 1.975 . 1) /2 = 0.9875 moles of O₂