CHEMISTRY DEPARTMENT

WAID ACADEMY

ENTHALPY

The enthalpy of combustion of methanol, CH3OH, is -715 kJ mol-1. The mass of methanol which has to be burned to produce 71.5 kJ is

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3.2 g 32g 71.5 g 715 g

1. 3.2 g

2. 32g

3. 71.5 g

4. 715 g

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A group of students added 6 g of ammonium chloride crystals to 200 cm3 of water at a temperature of 25oC.The enthalpy of solution of ammonium chloride is +13.6 kJ mol-1. After dissolving the crystals, the temperature of the solution would most likely be

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30oC. 27oC. 25oC. 23oC.

1. 30oC.

2. 27oC.

3. 25oC.

4. 23oC.

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Which equation illustrates an enthalpy of combustion?

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A. B. C. D.

1. A.

2. B.

3. C.

4. D.

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When 3.6 g of butanal (relative formula mass = 72) was burned, 134 kJ of energy was released.From this result, what is the enthalpy of combustion, in kJ mol-1?

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-6.7 6.7 -2680 2680

1. -6.72. +6.73. -26804. +2680

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The enthalpy of neutralisation in an acid/alkali reaction is always the energy released in

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the neutralisation of one mole of acid.

the neutralisation of mole of alkali.

the formation of one mole of salt.

the formation of one mole of water.

1. the neutralisation of one mole of acid.

2. the neutralisation of mole of alkali.

3. the formation of one mole of salt.

4. the formation of one mole of water.

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A potential energy diagram for a reaction is shown below.

The enthalpy change for the reaction is

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-361 kJ -227 kJ -91kJ +361kJ

1. -361 kJ2. -227 kJ3. -91kJ4. +361kJ

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Which set of data refer to the diagram shown below?

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A B C D

1. A

2. B

3. C

4. D

Enthalpy change = - 60 kJActivation energy = - 80 kJ

Enthalpy change = +80 kJActivation energy = - 60 kJ

Enthalpy change = +60 kJActivation energy = +80 kJ

Enthalpy change = -60 kJActivation energy = +80 kJ

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The enthalpy change for the forward reaction shown in the diagram opposite can be represented by

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x y x + y x-y

1. x

2. y

3. x + y

4. x-y

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When 0.1 g of an alcohol is burned the energy released increased the temperature of 200cm3of water from 23.1 oC to 34.2oC.Calculate the enthalpy change for this reaction in kJ mol-1.

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+ 4.64 kJ - 4.64 kJ - 9.28 kJ + 9.28 kJ

1. + 4.64 kJ

2. - 4.64 kJ

3. - 9.28 kJ

4. + 9.28 kJ

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When 0.01 mole of compound X is burned the energy given out raised the temperature of 250cm3 of water by 22.4oC.Calculate the enthalpy of combustion of compound X, in kJ mol-1.

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-0.936 -23.408 -234.08 -2340.8

1. - 0.936

2. - 23.408

3. - 234.08

4. - 2340.8

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