Enthalpy

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Flashcards on Enthalpy, created by I Shouldn't be awake on 24/04/2018.
I Shouldn't be awake
Flashcards by I Shouldn't be awake, updated more than 1 year ago
I Shouldn't be awake
Created by I Shouldn't be awake over 6 years ago
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Question Answer
What is H? Heat energy of a system
ΔH= H(products) - H(reactants)
ΔfHϴ ΔH When 1 MOLE compound formed from elements under ϴ
ΔfHϴ of an element 0
ΔcHϴ One mole compound completely reacted w/ O2 under ϴ
ΔneutHϴ Acid+Base = 1 MOLE H2O under ϴ
Effect of doubling vol. in ΔneutHϴ on T change Double T = double E however spread over twice the volume so no change
How is ΔrHϴ determined from q? q = E gained by surroundings So ΔrHϴ must be the opposite
What is m in reaction btw. 2 solutions? Solution itself is the immediate surroundings So M of both
What is C? 'C needed to ^ 1g substance by 1K
Inaccuracies w/ experimental ΔcHϴ (3) Incomplete combustion as CO or Soot Evaporation of methanol on wick Heat loss to surounding other than water
Δ btw. experimental and databook Experimental less exothermic due to less efficient energy transfer
How to increase accuracy (2) Use a draught screen could minimise erros of heat loss Input O2 gas ensure complete combustion
Proving that a reactant is in excess in ΔrHϴ Calculate n of limiting reagant This gives you n of excess required Calculate actual n of excess
Calculating ΔrH from bond enthalpies ΔrH=ΣH(r) - ΣH(p)
What conditions are required when working out these reactions? All species must be gaseous, therefore it can't be standard if say H2O is involved. Can still work out the standard, but would need to account for ΔrH of H2O(g) -> H2O(l)
What is average bond enthalpy E required to break 1 mole of bonds in a gaseous molecule
What is DeltarH from formation? P-R
What's enthalpy change of reaction from combustion? R-P
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