The chemical equation below shows the combustion of methane (CH4).

CH4 + 2O2 - > CO2 + 2H2O

The molar mass of oxygen gas (O2) is 32.00 g/mol. The molar mass of carbon dioxide (CO2) is 44.01 g/mol. What mass of CO2, in grams, will form when 8.94 g O2 completely react?

a: 3.25

b: 6.15

c: 13.0

d: 53.0

According to the chemical equation, the reaction ratio between O2 and CO2 is 2:1, which mean for every 2 moles of O2 reacted there is 1 mole of CO2 formed.

Use the molar mass and mass of O2 to find out the moles of O2: moles of O2 = mass of O2/molar mass of O2 = 8.94g/32.00g/mol = 0.2794 mole. Therefore, the moles of CO2 that formed is 0.2794moles/2 = 0.1397 mole

Use the moles and molar mass CO2 to find out the mass of CO2:

Mass of CO2 = moles of CO2 * molar mass of CO2 = 0.1397 mole *.44.01g/mole = 6.15 g.

So the answer is B 6.15g.