January 12 Chemistry 11

In todays class Mr Doktor started out by combing ammonium nitrate and water which made the beaker turn cold. This was an endothermic reaction. After he lighted the bunsen burner and burned magnesium the magnesium turned to light and this was an exothermic reaction. He then burned steel wool and there were sparks which was another example of an exothermic reaction.

We then took notes on heat and enthalpy
reactions that release heat are called exothermic
reactions that absorb heat are endothermic
heat is a form of energy all chemicals have energy stored in them stored energy is called enthalpy
the symbol for enthalpy is H

Exothermic reaction and Endothermic reaction:






To write Exothermic reactions it would be:
2C8H18 + 25O2 = 16CO2 + 18H2O + 5076 KJ
2C8H18 + 25O2 = 16CO2 + 18H2O H = -5076Kf exothermic = negative


For Endothermic it would be:
2C + 2H2 + 52.3 KJ = C2H4 52.3KJ
2C + 2H2 = C2H4 H = 52.3 KJ endothermic = positive

Coefficients can also stand for moles of molecules
N2 + 3H2 = 2NH3 + 46.3 kJ
1mol of N2 = 46.3 kJ
3 mol of H2 = 46.3 kJ
2 mol of NH3 = 46.3 kJ

Example: find the amount of heat produced if 5 mol of H2 are consumed when making ammonia.
46.3 kJ / 3mol H2 x 5 mol of H2 = 77kJ

Here is a video on Endothermic and Exothermic reactions: