A3 - Formation and Combustion Enthalpy Flashcards

1
Q

Define standard enthalpy of formation

A

The enthalpy change when one mole of a substance is formed from its elements under standard conditions

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2
Q

What is there always one mole of in an enthalpy of formation equation?

A

There is one mole of the substance being formed

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3
Q

What must a substance be formed from in an enthalpy of formation equation?

A

Its elements in their standard states

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4
Q

What substances have an enthalpy of formation of zero?

A

Elements in their standard states

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5
Q

What is the enthalpy of formation for an element in its standard state?

A

Zero

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6
Q

When would an element have an enthalpy of formation that is not zero?

A

When the element is not in its standard state

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7
Q

Which elements are diatomic?

A

H2, F2, Cl2, Br2, I2, O2, N2

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8
Q

What are standard conditions?

A

Temperature = 298 K. Pressure = 100 kPa

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9
Q

Define standard enthalpy of combustion

A

The enthalpy change when one mole of a substance is completely combusted under standard conditions

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10
Q

What type of combustion must happen when during an enthalpy of combustion?

A

Complete combustion

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11
Q

What are the products for an enthalpy of combustion?

A

CO2 and/or H2O

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12
Q

What substances have an enthalpy of combustion of zero?

A

CO2 and H2O

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13
Q

Why does CO have an enthalpy of combustion that is not zero?

A

Because CO is a product of incomplete combustion, so it can be combusted further

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14
Q

Why do CO2 and H2O have enthalpies of combustion of zero?

A

Because they are products of complete combustion and can’t be combusted

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15
Q

What is there always one mole of in an enthalpy of combustion equation?

A

There is one mole of the substance being combusted?

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16
Q

What is combustion?

A

A reaction with oxygen