3.1.4 Energetics Flashcards
Enthalpy
all the heat energy stored in a chemical system
Chemical system
all of the chemicals present in a chemical reaction
Are neutralisation reactions endo or exo?
exo
Equation for change in enthalpy
products-reactants
Draw the neutralisation enthalpy profile for the following reaction
HCL + NaOH→NaCL + H2O
endo or exo?
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EXO
Draw the enthalpy profile for the following reaction
CaCO3→CaO + CO2
endo or exo?
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ENDO
What are standard conditions
temp:298K or 25°c
pressure:100kPa
concentration:1moldm^-3
Units for standard enthalpy change
Kjmol^-1
Define standard enthalpy change of combustion
enthalpy change when one mole of a substance is completely burned with oxygen under standard conditions and all their chemicals are under their standard states
Define standard enthalpy change of neutralisation
enthalpy change when one mole of water is formed in a neutralisation reaction under standard conditions
What is the enthalpy change between any strong acid and alakli?
-57Kjmol^-1
Define standard enthalpy of formation
Enthalpy change when one mole of a compound is formed from its elemnets under standard conditions and all chmeicals are under their standard states
Define standard enthalpy change of reaction
When a reaction takes place in the molar quantities shown by the balanced chemical equation under standard conditions, all chemicals in their standard states
Have you practiced calculating enthalpies yet?
HMMMMMMMMMMMMMM? HMMMM? HMMM? 🤔 🤔 🤔
State Hess’s law
if a reaction cann be carried out via two different pathways, then the total enthalpy change for these two reactions will be the same provided that the starting and final conditions are the same for both pathways
What is average bond enthalpy?
energy needed to break one mole of a specific bond in a molecule in the gaseous state
is forming bonds exo or endo? what sign?
exo, -ve
