Enthalpy Flashcards

(15 cards)

1
Q

Exothermic

A

Heat energy is transferred from the system to the surroundings

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2
Q

Endothermic

A

Heat energy is transferred from the surrounds to the system

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3
Q

Draw an exothermic enthalpy profile diagram

A
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4
Q

Draw an endothermic enthalpy profile diagram

A
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5
Q

Standard enthalpy change of combustion

A

Enthalpy change that occurs when one mole of substance reacts completely with oxygen under standard conditions, with all reactants and products in their standard states.

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6
Q

Standaard enthalpy change of neutralisation

A

Enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O(l) under standard conditions, with all reactants and products in their standard states.

(value of this is the same for all neutralisation reactions)

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7
Q

Standard enthalpy change of reaction

A

Enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions.

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8
Q

Standard enthalpy change of formation

A

Enthalpy change that occurs when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states.

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9
Q

Standard conditions

A

pressure: 100kPa / 1 atmosphere
temperature: 298K / 25 deg. cels.
concentration: 1 mol dm-3

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10
Q

Why would the experimental enthalpy change of combustion value not be that accurate

A

-Heat loss to surroundings other than water
-Incomplete combustion takes place, forming carbon monoxide and carbon
-Evaporation of alcohol from wick
-Non-standard conditions

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11
Q

Hess’ law

A

If a reaction can take place by two routes, and the starting and finishing conditions are the same, the total enthalpy change is the same for each route.

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12
Q

Average bond enthalpy

A

Total energy required to break one mole of a specified type of bond in a gaseous molecule

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13
Q

Explain why some reactions are exothermic

A

-Bond breaking absorbs energy and bond making releases energy
-More energy released than absorbed

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14
Q

Explain why some reactions are endothermic

A

-Bond breaking absorbs energy and bond making releases energy
-More energy absorbed than released

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15
Q

Activation energy

A

Minimum amount of energy required for a reaction to take place

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