DF1:1 Getting Energy From Fuels Flashcards

1
Q

What is the enthalpy change of a reaction?

A

The heat change of a reaction at constant pressure.

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2
Q

What are the units for enthalpy change?

A

kJ/mol

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3
Q

What is the symbol for enthalpy change?

A

Delta H ^standard conditions

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4
Q

What are the standard conditions?

A

100kPa pressure and 298 Kalvin.

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5
Q

How do you work out Kalvin?

A

Degrees celcius + 273

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6
Q

What happens in an endothermic reaction?

A

Energy is absorbed from the surroundings.

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7
Q

What happens in an exothermic reaction?

A

Energy is released to the surroundings.

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8
Q

What does an enthalpy level diagram look like for an exothermic reaction?

A

The products are lower in energy than the reactants, enthalpy change is negative.

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9
Q

What does an enthalpy level diagram look like for an endothermic reaction?

A

The products are higher in energy than the reactants, enthalpy change is positive.

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10
Q

What is an example of an exothermic reaction and why?

A

Combustion, as heat is being lost into the surroundings.

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11
Q

What is an example of an endothermic reaction and why?

A

Thermal decomposition, as the compound is being broken down by heat and energy is absorbed when bonds are broken.

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12
Q

What is standard enthalpy change of reaction?

A

The enthalpy change of a reaction according to the molar quantities in the equation under standard conditions.

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13
Q

What is the symbol for standard enthalpy change of reaction?

A

Delta r H ^standard conditions.

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14
Q

What is standard enthalpy change of neutralisation?

A

The enthalpy change when an acid and alkali react to form one mole of water under standard conditions.

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15
Q

What is the symbol for standard enthalpy change of neutralisation?

A

Delta neut H ^standard conditions.

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16
Q

What is standard enthalpy change of combustion?

A

The enthalpy change when 1 mole of a substance is completely burned in oxygen to make CO2 and H2O under standard conditions.

17
Q

What is the symbol for standard enthalpy change of combustion?

A

Delta c H ^standard conditions.

18
Q

What is standard enthalpy change of formation?

A

The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions.

19
Q

What is the symbol for standard enthalpy change of formation?

A

Delta f H ^standard conditions.

20
Q

What reaction is breaking bonds?

A

Endothermic.

21
Q

What reaction is the forming of bonds?

A

Exothermic.

22
Q

What is bond dissociation enthalpy?

A

The energy needed per mole to break attractive forces in bonds in only gaseous compounds.

23
Q

Why do we work out the mean bond enthalpy?

A

Bonds of the same type don’t all have the same amount of energy.