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level: Level 1 of Enthalpy

Questions and Answers List

level questions: Level 1 of Enthalpy

QuestionAnswer
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 isexit so heat is given out to the surroundings so -x
An endothermic reaction isentrance so heat is taken in from the surroundings so +x
Progress of reaction endothermicproducts higher than reactants
P of R exothermicreactions 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 diagramDRAW THE ARROWS THE RIGHT WAY LABEL THE AXIS LABEL THE LINES WRITE THE DELTA H WITH UNITS
Key points for an enthaply profile diagramTHE 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 changespressure =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 enthalpybond 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 eqq=mc(triangle)t m= mass c=4.18 q= heatgained or loss t=change in temp
Lattice enthalpy definitionthe enthalpy change that acompanies the formation of one mole of ionic compound from its gaseous ions under standard conditions