Energy from fuels: notes and practice questions

Acid rain is primarily caused by the atmospheric reaction of water with oxides of certain elements. Which element, when combusted, produces an oxide that does not contribute to acid rain?

A. C

B. N

C. S

D. Mg

Ethanol ($C_2H_5OH$) is often blended with gasoline as a biofuel. What are the sole products of the complete combustion of ethanol?

A. Carbon monoxide and water

B. Carbon and water

C. Carbon dioxide and hydrogen

D. Carbon dioxide and water

Propane ($C_3H_8$) is a common fuel used in camping stoves. Its complete combustion releases a significant amount of energy. The standard enthalpy change of combustion of propane is $-2219.2 \text{ kJ mol}^{-1}$.

Calculate the energy released per gram of fuel when propane is completely burned.

A $-50.3 \text{ kJ g}^{-1}$

B $-44.1 \text{ kJ g}^{-1}$

C $-2219.2 \text{ kJ g}^{-1}$

D $50.3 \text{ kJ g}^{-1}$

Propane ($C_3H_8$) is a common fuel used in gas barbecues. When writing out the balanced chemical equation for the complete combustion of propane, using the smallest whole number ratios, how many moles of oxygen are required for every mole of propane?

A 3

B 4

C 5

D 6

Which statement correctly compares a major environmental impact of using coal versus natural gas (approximated as methane, $CH_4$) as a fuel?

A. Coal combustion does not produce any greenhouse gases.

B. Natural gas combustion is a major source of the sulfur dioxide that causes acid rain.

C. For the same amount of energy produced, coal combustion releases a greater mass of carbon dioxide.

D. Natural gas combustion produces solid particulates (soot) that contribute to smog.

A research team is investigating the efficiency of different biofuels. One experiment involves the incomplete combustion of ethanol ($C_2H_5OH$) in a limited oxygen environment, producing solid carbon (soot) and water.

The unbalanced equation for this reaction is:

$C_2H_5OH + \_O_2 \rightarrow \_C + \_H_2O$

When this equation is balanced using the smallest possible whole number ratios, what is the coefficient for $O_2$?

A 1

B 2

C 3

D 4

Nitrogen ($N_2$) and oxygen ($O_2$) are the two most abundant gases in the Earth's atmosphere. Why are they not classified as greenhouse gases?

A. Their bond vibrations do not involve a change in dipole moment.

B. They are elements with low molar masses.

C. They are transparent to ultraviolet radiation.

D. They do not have any polar covalent bonds.

The combustion of propane, $C_3H_8$, in a camping stove with insufficient oxygen results in a yellow, sooty flame. Which substances are the expected products of this incomplete combustion?

A. Carbon dioxide ($CO_2$) and water ($H_2O$)

B. Carbon monoxide ($CO$), carbon ($C$), and water ($H_2O$)

C. Carbon dioxide ($CO_2$) and hydrogen ($H_2$)

D. Carbon monoxide ($CO$) and carbon ($C$)

Catalytic converters are a crucial component in modern vehicles for reducing harmful emissions. Which of the following correctly identifies a pollutant removed by a catalytic converter and the corresponding product of its reaction?

Which statement represents a significant environmental concern associated with the large-scale production of biofuels?

A. Biofuels are non-renewable energy sources.

B. The combustion of biofuels releases significant amounts of sulfur dioxide.

C. Cultivation of crops for biofuels can compete with land use for food production.

D. Biofuels have a much higher energy density compared to fossil fuels.

Carbon dioxide, $\text{CO}_2$, acts as a greenhouse gas. Which statement explains why $\text{CO}_2$ absorbs infrared radiation?

A. Asymmetrical stretching and bending vibrations result in a change in dipole moment.

B. Symmetrical stretching vibrations result in a change in dipole moment.

C. Infrared radiation promotes electrons to higher energy levels.

D. The polar bonds give the molecule an overall permanent dipole moment.

The complete combustion of octane ($C_8H_{18}$), a component of gasoline, produces several substances. Which product is considered a primary contributor to the enhanced greenhouse effect?

A. Water ($H_2O$)

B. Carbon monoxide ($CO$)

C. Carbon dioxide ($CO_2$)

D. Sulfur dioxide ($SO_2$)

Which statement describes a key advantage of using biofuels, such as bioethanol, over fossil fuels?

A. They have a higher energy density, releasing more energy per unit mass.

B. Their production does not compete with land required for food crops.

C. They are considered carbon-neutral as the $CO_2$ released is reabsorbed by the plants grown for their production.

D. Their combustion is always complete, producing no carbon monoxide.

The combustion of octane ($C_8H_{18}$), a component of gasoline, can be incomplete in a car engine. Which list contains substances that could all be products of this reaction?

A. Carbon dioxide ($CO_2$) and water ($H_2O$) only

B. Carbon monoxide ($CO$) and hydrogen ($H_2$)

C. Carbon ($C$), carbon monoxide ($CO$), carbon dioxide ($CO_2$) and water ($H_2O$)

D. Butane ($C_4H_{10}$) and butene ($C_4H_8$)

Which is a non-renewable energy source?

A. Geothermal energy

B. Petroleum

C. Solar energy

D. Biomass

The use of bioethanol as a fuel is often considered to be carbon-neutral. Which statement provides the best reason for this?

A. The complete combustion of ethanol produces only water.

B. The carbon dioxide released by combustion is balanced by the carbon dioxide absorbed by the plants from which the fuel is derived.

C. Bioethanol does not contain any carbon atoms.

D. The process of fermentation to produce ethanol is an endothermic process.

Which energy source is classified as a fossil fuel?

A. Biomass

B. Natural gas

C. Hydrogen

D. Nuclear fission