The combustion of propane (#C_3H_8#) produces 248 of energy per mole of propane burned. How much heat energy will be released when 1 000 L of propane are burned at STP?

Question

Cameron Andrews · Accepted Answer

Approx......#10^5*kJ# are evolved...........

The following equation can be used to illustrate propane combustion: #C_3H_8(g) + O_2(g)rarr3CO_2(g) + 4H_2O(l) + 2220* kJ# Your question does not even mention UNITS. I took the heat of combustion values from this website. And, yes, I know that we would normally write #DeltaH_"combustion"^@=-2220*kJ*mol.# We KNOW that hydrocarbon combustion is exothermic, so we can represent energy, #Delta#, as a reaction PRODUCT, for the purposes of answering this question. And we have a #1000*L# of gas at #"STP"#, which of course we must treat as an ideal gas to get the molar quantity: #n=(PV)/(RT)=(1*cancel"bar"xx10^3*cancelL)/(8.31xx10^-2*cancel"bar"*cancel(K^(-1))*mol^(-1)*cancelLxx273*cancelK)# #=44*1/(mol)^-1=44*1/(1/(mol))=44*mol#. We have #DeltaH_"combustion"^@=-2220*kJ*mol^-1#, and so we multiply the molar quantity by #DeltaH_"combustion"^@# #=44*molxx-2220*kJ*mol^-1~=10^5*kJ# Note that I have made assumptions with respect to #"standard conditions"#, which might be different to those specified by your syllabus; the UK syllabus is different to IB is different to the USA syllabus. I have ASSUMED, #"1 bar pressure"#, and #273*K#.

Natalie Anton · Answer

undefined To find the amount of heat energy released when 1,000 L of propane are burned at STP, we need to convert the volume of propane to moles using the ideal gas law, then use the given energy release per mole to calculate the total energy released.

1. Convert 1,000 L of propane to moles using the ideal gas law: $PV = nRT$.
   - $P$ = pressure = 1 atm (STP conditions)
   - $V$ = volume = 1,000 L
   - $n$ = moles (unknown)
   - $R$ = ideal gas constant = 0.0821 L·atm/mol·K
   - $T$ = temperature = 273 K (STP conditions)
   - Solve for $n$.

2. Once you have the number of moles, multiply it by the energy release per mole of propane burned (248 kJ/mol) to find the total energy released.

3. Perform the calculations.