What volume of oxygen gas at 25c and 1.06 atm is needes to completely combust 5.41g of propane?

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First, balance the equation:

C3H8 + 7O2 --> 3CO2 + 4H2O

Now, find moles -- divide 5.41 g of propane by the molecular weight of propane to find moles of propane.

I get 0.123 but you will need to use at least three significant figures in the molecular weight.
Multiply this by 7 to find moles of O2

Now, how much volume does this occupy?

V = nRT/P
where
n = answer for O2 above
P = 1.06 atm
T = 298 K
and R is in units of L-atm/deg-mol. (This is 0.08206)

Solve for V

I get 19.9 L

As best I can tell, you forgot to account for the 7:1 ratio of oxygen to propane...Show more