U3-3-2 - Enthalpy of Combustion Flashcards

Part of the Chemical Energy topic from Unit 3 of Higher Chemistry, Chemistry in Society

1
Q

What is Eh?

A

Heat energy (in kJ)

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2
Q

What is c?

A

Specific heat capacity of water (4.18)

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3
Q

What is ∆T?

A

Change in temperature

Difference between starting and final temperature of water

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4
Q

What is m?

A

Mass of substance heated, in kg
(NOT mass of fuel!)

For water, 1000 cm3 = 1 kg

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5
Q

Suggest the greatest source of error in this experiment

A

Heat loss to surroundings

due to lack of heat shield

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6
Q

Suggest a piece of apparatus that can minimise heat loss to surroundings during combustion

A

Heat shield (or bomb calorimeter)

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7
Q

The energy released when 1 mole of a substance undergoes complete combustion.

A

Enthalpy of combustion

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8
Q

Ethanol has GFM = 46 g.

Burning 4.6 g released 136.7 kJ.

Write an expression to calculate the enthalpy of combustion for ethanol.

A

Use proportion to scale up energy to 1 mole of fuel

1 mole has mass = GFM

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9
Q

This equation does not represent the enthalpy of combustion. Why?

A

Must be complete combustion (products CO2 and H2O)

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10
Q

Enthalpy of combustion

A

The energy released when 1 mole of a substance undergoes complete combustion.

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