CHEMISTRY SHENANIGANS

Today, we went over the Molar Enthalpy and Combustion worksheet and did a lab. In our lab, we placed water in a can and lit a candle underneath for several minutes. Afterwards, with the measurements we took, we tried to make an educated guess of how much energy was released or absorbed in the experiment. It looked a lot like this:



Questions from the homework:

1. A car engine burns 250g of octane (C8H18). If 1.19x10^3 kJ of heat are produced, what is the molar enthalpy of the combustion of Octane?
Answer: 250g ÷ 114g/mol (of Octane) = 2.19 mol
1.19x10^3 kJ ÷ 2.19 mol = 543 kJ/mol

4. When ethanol C2H5OH is burned, heat is released. For every mole of ethanol burned, 1300 kJ of heat are released.
a) If 2.5g of ethanol are burnt, how much heat will be released?
Answer: 2.5g x mol/46g x 1300kJ/mol = 70.65 -> 71 kJ

Questions for practice:

ex. What is the molar enthalpy of CO2 (g) in the reaction for the burning of butane below?
2 C4H10 (l) + 13 O2 (g) 8 CO2 (g) + 10 H2O (g) H = -5315 kJ
Answer: Molar enthalpy, change in H = 5315 kJ ÷ 8 mol = 664 kJ / mol.