Propane, C3H8, is a hydrocarbon that is commonly used as a fuel for cooking?

Question

B. Calculate the volume of air at 25ºC and 1.00 atmosphere pressure that is needed to burn completely 15.0 grams of propane. Assume that oxygen has a density of 1.31 g/L at 25ºC and that air is 21.0% O2 by volume.

C. The heat of combustion of propane is –2,220 kJ/mol. Calculate the heat of formation, ΔHfº, of propane given that ΔHfº of H2O(l) = –285.3 kJ/mol and ΔHfº of CO2(g) = –393.5 kJ/mol.

D)Assume that all the heat given off in burning 20.0 grams of propane is transferred to a quantity of water (Cp = 4.184 J/g • K). The water increases in temperature from 18.0ºC to 37.0ºC. What volume (L) of water was heated

Answer 1

Start with a balanced equation

C3H8 + 5O2 == 3CO2 + 4H2O

For part a. convert the 15 g of propane to moles. Use the molar ratio to get moles of oxygen. Now use the ideal gas law, PV=nRT to convert the moles and solve for the volume of oxygen. Since air is 21% oxygen, you can finally calculate the volume of air.

I haven't done the part b in a long time so I'll pass on that

For part c. use q = mCp delta T. You will have q from part b. You have delta T and the Cp of water.. Now plug in and get the mass of water