Question

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)

Answer 1

.9875 moles O2

Step-by-step explanation:

First you need to balance the formula

2H2+O2⟶ 2H2O

Now you'll use the formula for stoichiometry

moles of known/1 * coefficient of unknown/coefficient of known= unknown moles

fill it in with the information given

1.975/1 * coefficient of O2 (1) / coefficient of H2 (2)

1.975 * 1/2= .9875 moles of O2

sig figs are already being used

Answer 2

0.9875 moles of O₂

Step-by-step 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