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CHEMISTRY, M4 EQ-Bank 1

Ethanol ) is a common hydrocarbon fuel used in alcohol burners. It combusts completely according to the following equation:

A student conducts an experiment to determine the heat energy released by ethanol during combustion.

They burn 0.25 g of ethanol in excess oxygen, capturing the heat released in a calorimeter containing 75.0 g of water. The water's temperature increases from 21.0 °C to 34.5 °C. Calculate the experimental molar heat of combustion for ethanol based on these results.   (3 marks)

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.

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Heat absorbed by the water :

Moles of ethanol burned:

Experimental molar heat of combustion:

CHEMISTRY, M4 EQ-Bank 38v4

Methanol () is a hydrocarbon fuel which combusts completely according to the following equation:

A chemist burns 0.40 g of methanol in excess oxygen during a calorimetry study, and the heat energy is used to heat 80.0 g of water. The initial temperature of the water in the calorimeter is 24.0 °C, which rises to a maximum of 52.0 °C after absorbing the energy from the combustion reaction. Based on these results, calculate the experimental molar heat of combustion () for methanol.   (4 marks)

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The experimental molar heat of combustion () for methanol is . (2 sig.fig.)

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Calculate the energy absorbed by the water:

Calculate the number of moles of methanol burned:

Calculate the molar heat of combustion:

→ The experimental molar heat of combustion () for methanol is . (2 sig.fig.)

CHEMISTRY, M4 EQ-Bank 38v3

Propane () is a hydrocarbon fuel which combusts completely according to the following equation:

A chemist burns 0.25 g of propane in excess oxygen during a calorimetry study, and the heat energy is used to heat 60.0 g of water. The initial temperature of the water in the calorimeter is 21.0 °C, which rises to a maximum of 42.0 °C after absorbing the energy from the combustion reaction. Based on these results, calculate the experimental molar heat of combustion () for propane.   (4 marks)

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The experimental molar heat of combustion () for propane is . (2 sig.fig.)

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Calculate the energy absorbed by the water:

Calculate the number of moles of propane burned:

Calculate the molar heat of combustion:

→ The experimental molar heat of combustion () for propane is . (2 sig.fig.)

CHEMISTRY, M4 EQ-Bank 38v2

Methane () is a hydrocarbon fuel which combusts completely according to the following equation:

A chemist burns 0.30 g of methane in excess oxygen during a calorimetry study, and the heat energy is used to heat 75.0 g of water. The initial temperature of the water in the calorimeter is 22.0 °C, which rises to a maximum of 36.5 °C after absorbing the energy from the combustion reaction. Based on these results, calculate the experimental molar heat of combustion () for methane.    (4 marks)

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The experimental molar heat of combustion () for methane is . (2 sig.fig)

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Calculate the energy absorbed by the water:

Calculate the number of moles of methane burned:

Calculate the molar heat of combustion:

→ The experimental molar heat of combustion () for methane is . (2 sig.fig)

CHEMISTRY, M4 EQ-Bank 2

Ethanol is a hydrocarbon fuel which combusts completely according to the following equation:

A chemist burns 0.50 g of ethanol in excess oxygen during a calorimetry study, and the heat energy is used to heat 100.0 g of water. The initial temperature of the water in the calorimeter is 20.0 °C, which rises to a maximum of 45.0 °C after absorbing the energy from the combustion reaction. Based on these results, calculate the experimental molar heat of combustion for ethanol.   (4 marks)

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Energy absorbed by the water:

Number of moles of ethanol burned:

Experimental molar heat of combustion:

CHEMISTRY, M4 2016 VCE 10a*

A senior Chemistry student created an experiment to calculate the molar heat of combustion of butane.

The experimental steps are as follows:

    1. Measure the initial mass of a butane canister
    2. Measure the mass of a metal can, add 250 mL of water and re-weigh.
    3. Set up the apparatus as in the diagram and measure the initial temperature of the water.
    4. Burn the butane gas for five minutes.
    5. Immediately measure the final temperature of the water.
    6. Measure the final mass of the butane canister when cool.
       

Results 

Quantity Measurement
mass of empty can 52.14 g
mass of can + water before combustion 303.37 g
mass of butane canister before heating 260.15 g
mass of butane canister after heating 259.79 g
initial temperature of water 22.1 °C
final temperature of water 32.7 °C

 

The balanced thermochemical equation for the complete combustion of butane is

  1. Calculate the amount of heat energy absorbed by the water when it was heated by burning the butane. Give your answer in kilojoules.   (2 marks)

  2. Calculate the experimental value of the molar heat of combustion of butane. Give your answer in kJ mol.   (2 marks)
  3. Use the known enthalpy change for butane to calculate the percentage energy loss to the environment.   (2 marks) 
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i.   

ii.   

iii.   

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i.   

 
   
   

 

ii.   


 

♦ Mean mark (ii) 42%.

iii.    

CHEMISTRY, M4 2014 VCE 3a*

The combustion of ethanol is represented by the following equation.

A spirit burner used 1.80 g of ethanol to raise the temperature of 100.0 g of water in a metal can from 25.0 °C to 40.0 °C.
 

Calculate the percentage of heat lost to the environment and to the apparatus.   (5 marks)

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CHEMISTRY, M4 2022 VCE 15 MC

The molar heat of combustion of glucose, , in the cellular respiration equation is 2805 kJ mol at standard laboratory conditions (SLC). The equation for cellular respiration is below.

Which one of the following statements about cellular respiration is correct?

  1. Cellular respiration is an endothermic reaction.
  2. The products of cellular respiration are water and carbon monoxide.
  3. Cellular respiration is a redox reaction because  accepts electrons from oxygen.
  4. When one mole of oxygen is consumed in the reaction, 467.5 kJ of energy is released.
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→ Chemical equation for respiration:

→ Exothermic redox reaction where is oxidised (loses electrons).

→ 6 mol of is required to produce 2805 kJ of energy.

→ 1 mol = 2805 ÷ 6 = 467.5 kJ of energy.

♦ Mean mark 47%.

CHEMISTRY, M4 2020 VCE 27 MC

The heat of combustion of ethanoic acid, , is –876 kJ mol and the heat of combustion of methyl methanoate, , is –973 kJ mol. The auto-ignition temperature (the temperature at which a substance will combust in air without a source of ignition) of ethanoic acid is 485°C and the auto-ignition temperature of methyl methanoate is 449°C.

Which one of the following pairs is correct?
 

 

A.  
B.
C.
D.
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→ Ethanoic acid converts less chemical energy to heat energy per mole (–876 kJ vs –973 kJ) indicating a lower chemical energy per mole.

→ Methyl methanoate’s lower autoignition temperature (449°C vs 485°C) indicates that a lower activation energy for combustion is needed.

♦ Mean mark 53%.

CHEMISTRY, M4 EQ-Bank 25

In an experiment, 1.40 g of pure sucrose, , underwent complete combustion, heating 350 mL of water from 19.6 °C to 35.8 °C.

= 342 g mol

Assuming there was no heat lost to the surroundings, calculate the experimental heat of combustion of pure sucrose, in joules per gram.   (2 marks)

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CHEMISTRY, M4 2005 HSC 17

  1. The heat of combustion of ethanol is 1367 kJ mol. In a first-hand investigation to determine the heat of combustion of ethanol, the experimental value differed from the theoretical value.
  2. Identify a reason for this difference.   (1 mark)

  3. Calculate the theoretical mass of ethanol required to heat 200 mL of water from 21.0°C to 45.0°C.   (2 marks)
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a.    Answers could include one of the following:

→ Heat loss into the surroundings from combustion process.

→ Specific examples of heat loss such as inefficient heating of water caused by proximity of the heat or not using a beaker lid.

b.   

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a.    Answers could include one of the following:

→ Heat loss into the surroundings from combustion process.

→ Specific examples of heat loss such as inefficient heating of water caused by proximity of the heat or not using a beaker lid.
 

b.   

CHEMISTRY, M4 2013 HSC 11 MC

The table shows the heat of combustion for four compounds.
 


 
 
   
   
   

Which of these compounds would produce the greatest amount of energy if 1.00 g of each is burnt?

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→ The smallest molecular mass it will result in the highest number of moles.

→ The highest number of moles gives the greatest amount of energy.

→ By comparing the molecular mass of each compound, the smallest is methane (.

CHEMISTRY, M4 EQ-Bank 21

The heat of combustion of propan-1-ol is 2021 kJ mol−1. Combustion takes place according to the equation:

What mass of water is formed when 1530 kJ of energy is released?   (2 marks)

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→ The stoichiometric ratio between propanol and water = 1 : 4

→ Moles of propane required if 1530 kJ of energy released:

CHEMISTRY, M4 2009 HSC 20

  1. Calculate the mass of ethanol that must be burnt to increase the temperature of 210 g of water by 65°C, if exactly half of the heat released by this combustion is lost to the surroundings.
  2. The heat of combustion of ethanol is 1367 kJ mol −1.  (3 marks)

  3. What are TWO ways to limit heat loss from the apparatus when performing a first-hand investigation to determine and compare heat of combustion of different liquid alkanols?  (1 mark)

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a.    3.85 grams

b.    Answers could include two of the following:

→ Use of an insulated vessel (Styrofoam cup)

→ Place the vessel as close as safely possible to the Bunsen’s flame.

→ Use a lid for the beaker

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a.   

Since half of the heat is lost to environmental surroundings.


 

b.    Answers could include two of the following:

→ Use of an insulated vessel (Styrofoam cup)

→ Place the vessel as close as safely possible to the Bunsen’s flame.

→ Use a lid for the beaker

CHEMISTRY, M4 2013 HSC 27

A 0.259 g sample of ethanol is burnt to raise the temperature of 120 g of an oily liquid, as shown in the graph. There is no loss of heat to the surroundings.
 

Using the information shown on the graph, calculate the specific heat capacity of the oily liquid. The heat of combustion of ethanol is 1367 kJ mol–1.   (4 marks)

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Mean mark 59%.