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Chemistry > Enthalpy Changes > Flashcards

Enthalpy Changes Flashcards

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1
Q

What is enthalpy?

A

A measure of the energy stored in a system

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2
Q

What is enthalpy change?

A

The heat energy exchange with its surroundings at constant pressure

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3
Q

What are the standard conditions?

A

Pressure of 100kPa
Temperature of 298k
Concentration of 1.0 moldm-3

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4
Q

What is standard state defined as?

A

The physical state of a substance under:
Pressure of 100kPa
Temperature of 298k

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5
Q

What is the standard enthalpy of reaction?

A

The enthalpy change accompanying a reaction in the molar quantities shown in a chemical equation
Under standard conditions with all substances in standard states

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6
Q

What is the standard enthalpy of formation?

A

The enthalpy change that takes place when 1 mole of a compound is formed from its elements
Under standard conditions with all substances in their standard states
Exothermic for ionic compounds

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7
Q

What is the standard enthalpy of formation of elements?

A

The enthalpy change that takes place when 1 mole of an element is formed from 1 mole of its elements
So there is no change

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8
Q

What is the standard enthalpy of combustion?

A

The enthalpy change taking place when 1 mole of a substance reacts completely with oxygen
Under standard conditions with all substances in their standard states

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9
Q

What is standard enthalpy of neutralisation?

A

The enthalpy change accompanying the reaction of an acid and a base to form 1 mole of water
Under standard conditions with all substances in their standard states

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10
Q

How can enthalpy change be calculated?

A

Calculate heat change:
q = mcDT
Calculate molar value:
DcH* = q/n KJmol-1

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11
Q

What is lattice enthalpy

A

The energy required to form 1 mole of a solid ionic lattice from its gaseous ions under standard conditions

It’s exothermic as energy released when ionic bonds formed

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12
Q

What is standard enthalpy of atomisation

A

1 mole of gaseous atoms is formed from its element in standard state under standard conditions

Endothermic as binds broken

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13
Q

What is first ionisation energy

A

1 mole of gaseous 1+ ions formed from gaseous atoms

Endothermic as e- lost must overcome nuclear attraction

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14
Q

What is second ionisation energy

A

1 mole of gaseous 2+ ions formed from gaseous 1+ ions

Endothermic and e- lost much overcome nuclear attraction

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15
Q

What is first electron affinity

A

1 mole of gaseous 1- ions is formed from gaseous atoms

Exothermic as e- attracted to nucleus

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16
Q

What is second electron affinity

A

1 mole of gaseous 2- ions formed from gaseous 1- ions

Endothermic as e- repelled by 1- ion it has to overcome

Chemistry (6 decks)

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