chemistry notes (energy from chemicals)
DESCRIPTION
Chemistry notes on Energy From Chemicals aka Energy ChangesTRANSCRIPT
Energy from Chemicals (aka Energy Changes) Enthalpy Change
o Exothermic H = negative Energy is given out, making surrounding hotter Examples
Combustion Dissolving of NaOH Most organic activities (respiration) Bond forming
o Endothermic H = positive Energy is taken in, making surrounding cooler Example
Photosynthesis Dissolving of NH4Cl Thermal decomposition Bond breaking
o Overall Overall enthalpy change depends on whether energy taken in by bond breaking
is greater/ lesser than energy given out by bond forming Not the number of bonds formed/ broken
Energy diagramso Energy level diagram
Only shows enthalpy changeo Energy profile diagram
Shows enthalpy change + activation energy Hydrogen fuel cell
o Obtained from electrolysis of water/ cracking of hydrocarbons (crude oil)o Reacts with oxygen to form water and generate electricity
Cathode : O2 (g) + 2 H2O (l) + 4 e- 4 OH- (aq) Anode : 2 H2 (g) + 4 OH- (aq) 4 H2O (l) + 4 e-
Overall : O2 (g) + 2 H2 (g) 2 H2O (l)
Nickolas Teo