| Hess's law basic rules | - combustion arrows= down
-formation = up
-read data not question
-clockwise=left |
| delta H = | H products -H reactants |
| An exothermic reaction is | exit so heat is given out to the surroundings so -x |
| An endothermic reaction is | entrance so heat is taken in from the surroundings so +x |
| Progress of reaction endothermic | products higher than reactants |
| P of R exothermic | reactions higher than products |
| examples of exothermic reactions | -oxidation of fuels
-respiration |
| Endothermic reactions examples | -Photosynthesis
- thermal decomposition of limestone |
| Key things to remember in a energy profile diagram | DRAW THE ARROWS THE RIGHT WAY
LABEL THE AXIS
LABEL THE LINES
WRITE THE DELTA H WITH UNITS |
| Key points for an enthaply profile diagram | THE SAME FOR ENERGY P DIAGRAM BUT DRAW THE ACTIVATION ENERGY SO AN EXTRA ARROW FROM THE REACTANTS TO TOP OF CURVES |
| What are the standard conditions for enthalpy changes | pressure =100kpa
temp is 298k
conc is 1 moldm-3 |
| standard enthalpy change of combustion | .... when one mole of a substance reacts completely with oxygen under standard conditions and all r and p in standard states |
| Standard enthalpy change of formation | ... takes place when one mole of a compound is formed from its consistent elements in their standard states under standard conditions |
| standard enthalpy change of neutralisation | .... the reaction of an acid by a base to form one mole of h20 under standard conditons with r and p in standard states |
| determine of solid and a solution | -mc(triangle)t
-calculate moles
- enthalpy change/moles depending on stoich |
| Bond enthalpy | bond enthalpy of broken/in - bond enthalpy of made/out |
| Hess's law basic rules | - combustion arrows= down
- formation arrows= up
-read the DATA not the question
-check stoich depending on what your working out
-CLOCKWISE FIRST on left side |
| Enthalpy change eq | q=mc(triangle)t
m= mass
c=4.18
q= heatgained or loss
t=change in temp |
| Lattice enthalpy definition | the enthalpy change that acompanies the formation of one mole of ionic compound from its gaseous ions under standard conditions |
