how many grams of butane must be burned in an excess of o2 gas in order to produce 7.64l of co2?

Answer 1

At what conditions? The volume of CO2 varies with both T and P. I'll assume STP.

2C4H10 + 13O2 ==> 8CO2 + 10H2O

mols CO2 = 7.64/22.4 = ?
Using the coefficients in the balanced equation, convert mols CO2 to mols C4H10.
Then convert mols C4H10 to grams. g = mols C4H10 x molar mass C4H10.