Question

How many moles of O2 (molar mass = 32.00 g/mol) are needed to react completely with 52.0 L of CH4 (g) at STP to produce CO2 and H2O? (molar mass of CH4 16.04 g/mol)

a. 11.6
b. 2.32
c. 4.64
d. 52.0

Answer 1

CH4 (g) + 2O2 (g) ---> CO2 (g) + 2H2O (l)
At STP, 1 mol gas = 22.4 L gas., so you have 52.0 L / 22.4 L/mol = 2.32 mol CH4.
According to the balanced reaction, you need 2 mol O2 for every 1 mol CH4. So you need 2 x 2.32 mol = 4.64 mol O2.

Choice C.