chem / energy.mdon commit [spec] start vector calculus (42fe40b)
   1# Chemical energy
   2
   3Chemical energy = heat content = enthalpy
   4
   5$$\Delta H = H_{\text{products}} - H_{\text{reactants}}$$
   6
   7**Exothermic** - energy released from system  
   8**Endothermic** - energy absorbed by system
   9
  10Must specify states (latent heat)
  11
  12## Thermochemical equations
  13
  14$\Delta H$ notates energy change (i.e. kJ / mol)  
  15Exothermic - negative $\Delta H$
  16
  17## Calorimetry
  18
  19$$E = mc \Delta T$$
  20
  21$$\text{calibration factor} = {E \over \Delta T} = {VIt \over \Delta T} \quad \text{J/K}$$
  22
  23## Fuels
  24
  25Substance used for energy production by **combustion** (exothermic)  
  26Fossil fuels - decaying organic material (e.g. coal, petrol, nat. gas)
  27
  28Crude oil - mixture of alkanes  
  29Derivatives:
  30
  31- petrodiesel (12-24 carbons / molecule)
  32- LPG
  33- nat. gas
  34
  35### Efficiency
  36
  37$$\text{% efficiency} = {\text{energy obtained in desired form} \over \text{energy available before conversion}} \times 100$$
  38
  39### Refining crude oil
  40
  41**Fractional distillation** - liquid is separated based on boiling point. B.P $\propto$ molecular size.
  42
  431. Separation column has temperature gradient (cooler at top)
  442. Crude oil is heated and injected at base
  453. Some components vapourise and rise
  464. When they reach $h$ where $T_{\text{ambient}}(h)=T_{\text{boiling}}$, they condense
  475. Trays catch falling condensed liquid
  48
  49![](graphics/fractional-distillation.png)
  50
  51### Biodiesel
  52
  53- made from animal & plant fats
  54- fats are esters between carboxylic acids (fatty acids) and glycerol.
  55- produced by reacting fats (triglycerides) with alcohol