>>12032334Ok so these words sound similar but they're not that similar. Enthalpy is change in energy. What this means is that if a reaction releases 50kJ of chemical energy, the enthalpy will be NEGATIVE 50kJ, because the reactants REALEASED 50kJ. Endothermic reactions which absorb "heat", meaning energy in this context, have a positive enthalpy. You can also measure MOLAR ENTHALPY. Molar enthalpy is used to discuss the nature of a reaction in general rather than a specific instance. Say you wanted to have some information on how much energy is released when CH4 and O2 make CO2 and H2O. First of all: REMEMBER TO bALANCE YOUR FUCKING EQUATION. CH4 and CO2 both have one carbon, H2O has half the hydrogen of CH4, so we have CH4 + ?O2 = CO2 + 2H2O, two moles of O2 will complete the balance: CH4 + 2O2 = CO2 + 2H2O. Now find a table of "heat of formation" that has all of your chemicals, measured in ENERGY PER MOLE. Heat of formation is energy change MEASURED RELATIVE TO PURE ELEMENTS (meaning that pure elements e.g. O2 have a value of exactly 0kJ/mol). If should release the same amount of energy to produce the same amount of CO2 and H2O out of the same amount of hydrogen, oxygen, and carbon, in different ways. The first way, direct combination, is what the values in the table signify. But making methane and then reacting it with oxygen should have the same net energy change, or else it would violate conservation of energy, so what you can do to calculate the MOLAR ENTHALPY by taking the heat of formation of the products (with their number of moles as coefficients) and subtract the same thing for the reactants, and what your doing is taking A to C, and subtracting A to B, and since A to B plus B to C has to equal A to C, A to C minus A to B IS REQUIRED BY THE LAWS OF PHYSICS to give you B to C, the molar enthalpy of your reaction. You can also do a similar process with individual bond energies. I don't understand entropy cause my teachers just gave me a bunch of formulae.
