3.2 Heat of Combustion

3.2 Heat of Combustion - Set 1

Report 1 / 5

The energy level diagram represents the burning of methane in excess oxygen gas.

Which of the following is true?

I.		The reaction releases heat to the surrounding.

II.		The reaction is an endothermic reaction.

III.		The heat of the reaction is \(\text{- 394 000 J}\).

IV.		The energy of products is higher than the energy of reactants.

I & IV
I & III
II & III
III & IV

Difficulty Level: Hard

3.2 Heat of Combustion - Set 1

Report 2 / 5

Fuel	Heat of Combustion
Methane	\(X\)
Butane	\(Y\)

Based on the table, which of the following is correct regarding the heat of combustion of methane and butane?

X > Y
X < Y
X = Y

Difficulty Level: Easy

3.2 Heat of Combustion - Set 1

Report 3 / 5

\(C_6H_{14} + \dfrac{19}{2}O_2 \rightarrow 6CO_2 + 7H_2O\\ \Delta H= \text{-2976 kJ mol}^{-1}\)

The combustion of hexane heats up \(\text{400 cm}^3\) of water.

What is the temperature change for combustion of hexane in excess oxygen gas to produce \(\text{28.7 kJ}\) of energy?

[Specific heat capacity of solution= \(4.2 \, J \, g^{-1}\,^OC^{-1}\), Density of solution= \(1.0 \,g\,cm^{-3}\)]

(A)		\(\text{15.08}^\text{O}\text{C}\)

(B)		\(\text{17.08}^\text{O}\text{C}\)

(C)		\(\text{16.08}^\text{O}\text{C}\)

(D)		\(\text{14.08}^\text{O}\text{C}\)

Difficulty Level: Hard

3.2 Heat of Combustion - Set 1

Report 4 / 5

The heat of combustion obtained from an experiment is normally less than the theoretical value.

Which precaution can be taken to increase the accuracy of the result?

Light the wick before placing the lamp under the container.
Stir the water continuously throughout the experiment.
Heat the water in a glass beaker.
Weigh the lamp when it is cold.

Difficulty Level: Medium

3.2 Heat of Combustion - Set 1

Report 5 / 5

The combustion of \(\text{4 g}\) propanol heats up \(\text{100 cm}^3\) of water.

The temperature of the water shows an increase of \(\text{11}^\text{O}\text{C}\).

Which of the following shows the correct amount of heat absorbed by the water and the heat of combustion of propanol?

[Specific heat capacity of water= \(4.2 \, J \, g^{-1}\,^OC^{-1}\), Density of water= \(1.0 \,g\,cm^{-3}\); Relative atomic mass: \(\text{C= 12, H= 1, O= 16}\)]

	Heat absorbed	Heat of combustion
(A)	\(\text{4 620 kJ}\)	\(\text{-66 kJ mol}^{-1}\)
(B)	\(\text{4 620 J}\)	\(\text{+66 kJ mol}^{-1}\)
(C)	\(\text{4 620 J}\)	\(\text{-66 kJ mol}^{-1}\)
(D)	\(\text{462 J}\)	\(\text{-66 kJ mol}^{-1}\)

Difficulty Level: Hard