Enthalpy change

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What is enthalpy?
H - is the heat content stored in a chemical system
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What is the law conservation
When heat is released from a chemical system the energy that leaves a chemical system system is the same energy that is gained by the surroundings
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What is enthalpy change?
ΔH - the heat exchange wih the surroundings during a chemical reaction at a constant pressure in it's standard state
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What is an exothermic reaction?
A reaction where the bond enthalpy of the products is lower than the bond enthalpy of the products - thus giving out energy in the form of heat
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What are examples of exothermic reactions? ΔH -
Combustion and respiration
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What is an endothermic reaction? ΔH +
The bond enthalpy of the products is greater than the bond enthalpy of the products - therefore energy is taken into the chemical system
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What is the activation energy?
The minimum amount of energy required to start a reaction by the breaking of bonds
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What are the standard conditions?
100kPa, 1moldm^3, -298K
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What must an equation have?
Standard states - solid, liquid, gas
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What is the standard enthalpy change of reaction?
Standard enthalpy change of reaction is the enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
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What is the standard enthalpy change of combustion?
Standard enthalpy change of combustion is the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactants being in their standard states
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What is the standard enthalpy change of formation?
Standard enthalpy change of formation is the enthalpy change that takes place when one mole of an ionic compound is formed from its constituent elements in their standard states, under standard conditions
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How do you work out enthalpy change?
Q=mcΔT (Joules) m=mass of water c=specific heat capacity and ΔT= energy change
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Card 2

Front

What is the law conservation

Back

When heat is released from a chemical system the energy that leaves a chemical system system is the same energy that is gained by the surroundings

Card 3

Front

What is enthalpy change?

Back

Preview of the front of card 3

Card 4

Front

What is an exothermic reaction?

Back

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Card 5

Front

What are examples of exothermic reactions? ΔH -

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