Question

The molar mass of oxygen gas (O2) is 32.00 g/mol. The molar mass of C3H8 is 44.1 g/mol.

What mass of O2, in grams, is required to completely react with 0.025 g C3H8?

0.018
0.034
0.045
0.091

Answer 1

Answer: D 0.091

Explanation: Edge 2023

Answer 2

the balanced chemical equation for the reaction is as follows;
C₃H₈ + 5O₂ ---> 3CO₂ + 4H₂O

stoichiometry of C₃H₈ to O₂ is 1:5

number of moles of C₃H₈ reacted - 0.025 g / 44.1 g/mol = 0.000567 mol according to molar ratio of 1:5
number of O₂ moles required are 5 times the amount of C₃H₈ moles reacted therefore number of O₂ moles required - 0.000567 x 5 = 0.00284 mol .
mass of O₂ required - 0.00284 mol x 32.00 g/mol = 0.091 mol .
answer is 0.091 mol