Help me pleaseee C3H8 (g) + 5 O2 (g)
->
3 CO2 (g) + 4 H2O (9)

1. Use stoichiometry to determine how many moles of O2 are needed
to completely react with 2.25 moles of C3H8.

11.25 moles of will be required to completely react with 2.25 moles of .

Explanation:

The balanced chemical equation is:

According to stoichiometry :

1 mole of require = 5 moles of

Thus 2.25 moles of will require=  of  

Thus 11.25 moles of will be required to completely react with 2.25 moles of .