3.2.5 Heat of Combustion – OnlineTuition.com.my

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Question 1 of 11

1. Question
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Combustion of propane in excess oxygen can be represented by the equation
below.

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O ∆H = -y kJ/mol

Which of the following statements are true?
- I. y kJ of heat energy is released for every mole of propane burnt.
- II. Heat is absorbed during the formation of carbon dioxide and water molecules.
- III. The energy content of reactants is less than that of the products.
- IV. Combustion of 1 dm³ of propane gas releases 3 dm³ carbon dioxide gas.
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Question 2 of 11

2. Question
1 point(s)
The figure shows the set-up of apparatus to determine heat of combustion of ethanol. A student found that the heat of combustion obtained is less than the theoretical value. What can be done to improve the experimental value?
- I. Use more water.
- II. Remove the wire gauze
- III. Place wind shields around the apparatus.
- IV. Use copper container instead of beaker
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Question 3 of 11

3. Question
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The burning of 0.6 g of X causes the temperature of 100 cm³ water to increase by 12^oC. What is the heat of combustion of X?
[ relative molecular mass of X = 60; specific heat capacity of water = 4.2 J g^{-1 o}C^-1]
- 504.0 kJ mol⁻¹
- 302.4 kJ mol⁻¹
- 72.0 kJ mol⁻¹
- 50.4 kJ mol⁻¹
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Question 4 of 11

4. Question
1 point(s)
A student carries out an experiment to determine the heat of combustion of propanol. Which of the following information does he need in order to calculate the heat of combustion?
- I Mass of water
- II Mass change of propanol
- III Initial temperature of propanol
- IV Highest temperature of water
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Question 5 of 11

5. Question
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C + O₂ → CO₂ ∆H = -393.5 kJ mol⁻¹

The equation above represents the reaction of formation of carbon dioxide. How much energy is released when 66g of carbon combust completely in excess oxygen. (Relative atomic mass: C:12; O:16 )
- 590.2kJ
- 196.7kJ
- 2164.2kJ
- 393.5kJ
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Question 6 of 11

6. Question
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C₃H₈ + 5O₂ → 3CO₂ + 4H₂O ∆H = -2220 kJ mol⁻¹

Find the mass of propane combusted, in excess of oxygen, to release 999 kJ of heat energy. (Relative atomic mass: C:12; O:16; H:1 )
- 19.8g
- 0.45g
- 44g
- 22g
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Question 7 of 11

7. Question
1 point(s)
Referring to the graph above, find the heat release if 6g propanol is combusted. (Relative molecular mass: Carbon = 12; Hydrogen = 1, Oxygen = 16)
- 2020kJ
- 202kJ
- 710kJ
- 138kJ
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Question 8 of 11

8. Question
1 point(s)
Alcohol Combustion heat (kJ/mol)

Methanol -710

Ethanol -1370

Propanol -2015

Pentanol -3300

Table above shows the heat of combustion for different alcohol. Estimate the heat of combustion of butanol.
- -3300 kJ/mol
- -1650 kJ/mol
- -2700 kJ/mol
- -2400kJ/mol
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Question 9 of 11

9. Question
1 point(s)
Which of the following hydrocarbons has the greatest heat of combustion?
- ethane
- propane
- butane
- pentane
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Question 10 of 11

10. Question
1 point(s)
A student carried out an experiment to determine the heat of combustion of an alcohol. The setup of the apparatus is shown in the figure above. He found that the heat of combustion obtained is much lower than the actual value. Which of the following could be the factor contributing to the error?
- I. Incomplete combustion of the alcohol
- II. Heat lost to the surrounding
- III. Lost of alcohol through evaporation
- IV. Lost of water through evaporation
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Question 11 of 11

11. Question
1 point(s)
The thermochemical equation below shows the combustion reaction between hexane and oxygen

What is the minimum mass of hexane need to be burnt to produce heat that can heat up 5 kg of water from 30 degrees to 100 oC?
- 42.00g
- 36.12g
- 86.00g
- 14.70g
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Alcohol	Combustion heat (kJ/mol)
Methanol	-710
Ethanol	-1370
Propanol	-2015
Pentanol	-3300