Question 1

Why are many bond enthalpies described as averages?

  A  

they are averaged out over many molecules with different kinetic energies

  B  

they are averaged out over different compounds containing the same bond

  C  

they are the averages of the bond in liquid and gaseous compounds

  D  

they are average values from different data books

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Question 2

What is the definition of the bond energy of the Br-Br covalent bond?

  A  

the energy required to produce one mole of bromine atoms in the gaseous state

  B  

the energy required to produce one mole of bromine atoms in the liquid state

  C  

the energy required to break one mole of Br-Br bonds in the gaseous state

  D  

the energy required to break one mole of Br-Br bonds in the liquid state

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Question 3

Propanone has the molecular formula C3H6O.

The enthalpy change of combustion of hydrogen is -286 kJ mol-1.

The enthalpy change of combustion of carbon is -394 kJ mol-1.

The enthalpy change of combustion of propanone is -1,786 kJ mol-1.

Using this information, what is the enthalpy change of formation of propanone?

  A  

-1,106 kJ mol-1

  B  

-540 kJ mol-1

  C  

-254 kJ mol-1

  D  

+1,106 kJ mol-1

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Question 4

A butane burner is used to heat water. The Mr of butane is 58.

● ΔHc of butane is -2,877 kJ mol-1.

● 250 g of water is heated from 12°C to 100°C.

● The burner transfers 47% of the heat released from the burning fuel to the water.

Assume that the butane undergoes complete combustion and none of the water evaporates.

What is the minimum mass of butane that must be burnt?

  A  

0.068 g

  B  

1.85 g 

  C  

3.94 g

  D  

4.48 g

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Question 5

Which equation represents the standard enthalpy change of formation of water?

  A  

H2(g) + 0.5O2(g) ➔ H2O(g)

  B  

H2(g) + 0.5O2(g) ➔ H2O(l)

  C  

2H2(g) + O2(g) ➔ 2H2O(g)

  D  

2H2(g) + O2(g) ➔ 2H2O(l)

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Question 6

200 g of water are at 25°C.

The water is heated to 75°C by burning 2 g of ethanol.

What is the amount of energy transferred to the water?

  A  

0.418 kJ 

  B  

10.4 kJ 

  C  

41.8 kJ

  D  

62.7 kJ

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Question 7

Which expression gives the standard enthalpy change of combustion of methane?

  A  

ΔHf(CH4) + ΔHf(CO2) - 2ΔHf(H2O)

  B  

ΔHf(CO2) + 2ΔHf(H2O) + ΔHf(CH4)

  C  

ΔHf(CH4) + 2ΔHf(H2O) - ΔHf(CO2)

  D  

ΔHf(CO2) + 2ΔHf(H2O) - ΔHf(CH4)

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Question 8

A student mixed 25.0 cm3 of 4.00 moldm-3 hydrochloric acid with an equal volume of 4.00 mol dm-3 sodium hydroxide. The initial temperature of both solutions was 15°C. The maximum temperature recorded was 30°C.

Using these results, what is the enthalpy change of neutralisation of hydrochloric acid?

  A  

-62.7 kJ mol-1

  B  

-31.4 kJ mol-1

  C  

-15.7 kJ mol-1

  D  

-3.14 kJ mol-1

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Question 9

All the reactants and products of an exothermic reaction are gaseous.

Which statement about this reaction is correct?

  A  

the total bond energy of the products is less than the total bond energy of the reactants, and ΔH for the reaction is negative

  B  

the total bond energy of the products is less than the total bond energy of the reactants, and ΔH for the reaction is positive

  C  

the total bond energy of the products is more than the total bond energy of the reactants, and ΔH for the reaction is negative

  D  

the total bond energy of the products is more than the total bond energy of the reactants, and ΔH for the reaction is positive

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Question 10

Gaseous phosphorus pentachloride can be decomposed into gaseous phosphorus trichloride and chlorine by heating. The table gives the bond energies.

What is the enthalpy change for the decomposition of PCl5 to PCl3 and Cl2?

  A  

-418 kJ mol-1

  B  

-88 kJ mol-1

  C  

+88 kJ mol-1

  D  

+418 kJ mol-1

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Question 11

Hydrogen and chlorine react as shown below.

H2(g) + Cl2(g) ➔ 2HCl(g)       ΔH = -184.6 kJ mol-1

Which statement about this reaction is correct?

  A  

less energy is released on bond making than is taken in during bond breaking

  B  

the enthalpy change for the reverse equation is +184.6 kJ mol-1

  C  

the enthalpy change of formation of HCl(g) is -184.6 kJ mol-1

  D  

the temperature decreases during the reaction

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Question 12

Some enthalpy data is given in the table below.

Use the information in the table and the stated enthalpy change to calculate the missing bond enthalpy.

  A  

234

  B  

1,064

  C  

1,476

  D  

1,936

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Question 13

Which reaction has an enthalpy change equal to the standard enthalpy of formation of silver iodide?

  A  

Ag(g) + 0.5I2(g) ➔ AgI(s)

  B  

Ag(s) + 0.5I2(s) ➔ AgI(s)

  C  

Ag+(g) + I-(g) ➔ AgI(s)

  D  

Ag+(aq) + I-(aq) ➔ AgI(s)

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Question 14

Nitrogen dioxide is produced from ammonia and air as shown in these equations

4NH3(g) + 5O2(g) ➔ 4NO(g) + 6H2O(g)     ΔH = -909 kJ mol-1

2NO(g) + O2(g) ➔ 2NO2(g)                          ΔH = -115 kJ mol-1

What is the enthalpy change (in kJ mol-1) for the following reaction?

4NH3(g) + 7O2(g) ➔ 4NO2(g) + 6H2O(g)

  A  

-679

  B  

-794

  C  

-1,024

  D  

-1,139

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Question 15

What is the enthalpy of formation of buta-1,3-diene, C4H6(g)?

  A  

+112  kJ mol-1

  B  

-112 kJ mol-1

  C  

+746 kJ mol-1

  D  

-746 kJ mol-1

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