# Energetics

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Define Enthalpy Change
The heat energy transferred in a reaction at constant temperature and pressure
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Define Standard Enthalpy of Formation
The enthalpy change when one mole of a substance is formed from its elements. All reactants and products in their standard states under standard conditions
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Define Standard Enthalpy of Combustion
The enthalpy change when one mole of a substance is combusted completely in oxygen. All reactants and products in their standard states under standard conditions
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Define Mean Bond Enthalpy
The average enthalpy change needed to break a covalent bond, averaged over a large number of different molecules
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How do you calculate enthalpy change given bond enthalpy data?
BERP Reaction = Reactants - Products
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How do you calculate enthalpy change given formation data?
FliPpeR Reaction = Products - Reactants
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How do you calculate enthalpy change given combustion data?
CRoPs Reaction = Reactants - Products
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Define Hess's Law
The enthalpy change of a reaction is independent of the route taken provided the conditions are kept the same
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What is the value of the enthalpy of formation for elements? Why?
0 - because there is no change
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Why is it not possible to measure the enthalpy change for combustion reactions?
Cannot ensure that complete/incomplete combustion always occurs
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## Other cards in this set

### Card 2

#### Front

The enthalpy change when one mole of a substance is formed from its elements. All reactants and products in their standard states under standard conditions

#### Back

Define Standard Enthalpy of Formation

### Card 3

#### Front

The enthalpy change when one mole of a substance is combusted completely in oxygen. All reactants and products in their standard states under standard conditions

### Card 4

#### Front

The average enthalpy change needed to break a covalent bond, averaged over a large number of different molecules

### Card 5

#### Front

BERP Reaction = Reactants - Products