Calculate the energy released, in $\mathrm{kJ}$, from the complete combustion of $5.00 {\mathrm{dm}}^3$ of ethanol.

State a class of organic compounds found in gasoline.

Outline the advantages and disadvantages of using biodiesel instead of gasoline as fuel for a car. Exclude any discussion of cost.

A mixture of gasoline and ethanol is often used as a fuel. Suggest an advantage of such a mixture over the use of pure gasoline. Exclude any discussion of cost.

When combusted, all three fuels can release carbon dioxide, a greenhouse gas, as well as particulates. Contrast how carbon dioxide and particulates interact with sunlight.

Methane is another greenhouse gas. Contrast the reasons why methane and carbon dioxide are considered significant greenhouse gases.

Suggest a wavenumber absorbed by methane gas.

Determine the relative rate of effusion of methane ($M_{\mathrm{r}}=16.05$) to carbon dioxide ($M_{\mathrm{r}}=44.01$), under the same conditions of temperature and pressure. Use section 1 of the data booklet.

The Geobacter species of bacteria can be used in microbial fuel cells to oxidise aqueous ethanoate ions,
CH₃COO⁻(aq), to carbon dioxide gas.

State the half-equations for the reactions at both electrodes.

A concentration cell is an example of an electrochemical cell.

(i) State the difference between a concentration cell and a standard voltaic cell.

(ii) The overall redox equation and the standard cell potential for a voltaic cell are:

Zn (s) + Cu²⁺ (aq) → Zn²⁺ (aq) + Cu (s)     E^θ_cell = +1.10 V

Determine the cell potential E at 298 K to three significant figures given the following concentrations in mol dm⁻³:

[Zn²⁺] = 1.00 × 10⁻⁴       [Cu²⁺] = 1.00 × 10⁻¹

Use sections 1 and 2 of the data booklet.

(iii) Deduce, giving your reason, whether the reaction in (b) (ii) is more or less spontaneous than in the standard cell.

Dye-sensitized solar cells (DSSC) convert solar energy into electrical energy.

(i) Describe how a DSSC converts sunlight into electrical energy.

(ii) Explain the role of the electrolyte solution containing iodide ions, I⁻, and triiodide ions, I₃⁻, in the DSSC.

Show that the mass of the ²³⁸U isotope in the rock is $0.639 \mathrm{kg}$.

The half-life of ²³⁸U is $4.46\times {10}^9$ years. Calculate the mass of ²³⁸U that remains after $0.639 \mathrm{kg}$ has decayed for $2.23\times {10}^{10}$ years.

Outline a health risk produced by exposure to radioactive decay.

Deduce the nuclear equation for the decay of uranium-238 to thorium-234.

Thorium-234 has a higher binding energy per nucleon than uranium-238. Outline what is meant by the binding energy of a nucleus.

Determine the nuclear binding energy, in $\mathrm{J}$, of ${}_{238}\mathrm{U}$ using sections 2 and 4 of the data booklet.

The mass of the ${}_{238}\mathrm{U}$ nucleus is $238.050786 \mathrm{amu}$.

Identify two ways in which the structure of the dye shown resembles the chlorophyll molecule. Use section 35 of the data booklet.

Both photosynthesis and the Grätzel cell use energy from sunlight to bring about reduction. Deduce an equation for the reduction reaction in the electrolyte of a Grätzel cell.

Doping of silicon increases the conductivity in semiconductors.

Describe the doping in p-type and n-type semiconductors.

Doping of silicon increases the conductivity in semiconductors.

Explain how doping improves the conductivity of silicon.

The structures of 11-cis-retinal and β-carotene are given in section 35 of the data booklet. Suggest a possible wavelength of light absorbed by each molecule using section 3 of the data booklet.

The natural absorption of light by chlorophyll has been copied by those developing dye-sensitized solar cells (DSSCs). Outline how a DSSC works.

Deduce the half-cell equations occurring at each electrode during discharge.

Outline the function of the proton-exchange membrane (PEM) in the fuel cell.

Explain how the flow of ions allows for the operation of the fuel cell.

The mass of X is 8.005305 amu and that of ${}_2^4\text{He}$ is 4.002603 amu. Determine the energy produced, in J, when one atom of ${}_6^{12}\text{C}$ is formed in this reaction. Use section 2 of the data booklet.

Contrast how absorption of photons and charge separation occur in each device.

Suggest one advantage a DSSC has over a silicon based photovoltaic cell.

Complete the half-equations on the diagram and identify the species moving between the electrodes.

State the factor that limits the maximum current that can be drawn from this cell and how electrodes are designed to maximize the current.

Explain how the proportion of ²³⁵U in natural uranium is increased.

Deduce half-equations for the reactions at the two electrodes and hence the equation for the overall reaction.

Suggest a way in which they are similar.

Outline the difference between primary and rechargeable cells.

Identify one factor that affects the voltage of a cell and a different factor that affects the current it can deliver.

Calculate the loss in mass, in kg, and the energy released, in J, when 0.00100 mol of ²²⁸Ac decays, each atom losing an electron. Use section 2 of the data booklet and E = mc².

²²⁸Ac → ${}_{-1}^0\text{e}$ + ²²⁸Th

Determine the energy released, in J, by 0.00100 mol of ²²⁸Ac over the course of 18 hours.

Outline how nuclear ionising radiation can damage DNA and enzymes in living cells.

Draw the Lewis (electron dot) structure for an appropriate doping element in the box in the centre identifying the type of semiconductor formed.

State the feature of the molecules responsible for the absorption of light.

Outline why complex B absorbs light of longer wavelength than complex A.

Fuel cells have a higher thermodynamic efficiency than octane. The following table gives some information on a direct methanol fuel cell.

Determine the thermodynamic efficiency of a methanol fuel cell operating at 0.576 V.

Use sections 1 and 2 of the data booklet.

Describe the effect of infrared (IR) radiation on carbon dioxide molecules.

Outline one approach to controlling industrial emissions of carbon dioxide.

Outline the major technical problem affecting the direct use of vegetable oils as fuels in internal combustion engines and the chemical conversion that has overcome this.

State the formula of a fuel that might be produced from the vegetable oil whose formula is shown.

Early photovoltaic cells were based on silicon containing traces of other elements. State the type of semiconductor produced by doping silicon with indium, In, giving a reason that refers to its electronic structure.

Dye-sensitized solar cells, DSSCs, use a dye to absorb the sunlight. State two advantages that DSSCs have over traditional silicon based photovoltaic cells.

The structure of two dyes used in DSSCs are shown.

Predict, giving a reason, which dye will absorb light of longer wavelength.

Suggest another advantage and one disadvantage of solar energy.

State a physical property of vegetable oils that makes them very difficult to use as fuel in internal combustion engines.

Describe how vegetable oils can be converted to a more suitable fuel.

Contrast the importance of carbon dioxide and methane as greenhouse gases.

Explain, using an equation, the effect of increased carbon dioxide in the atmosphere on the pH of lake water.

Formulate equation(s) for the conversion of coal and steam to methane.

Comment on the specific energies of hydrogen and methane.

Calculate the mass, in kg, of carbon dioxide produced by the complete combustion of 72.0 dm³ octane, C₈H₁₈.

Density of C₈H₁₈ = 703 g dm⁻³

C₈H₁₈ (l) + 12.5O₂ (g) → 8CO₂ (g) + 9H₂O (g)

Explain fusion reactions with reference to binding energy.

Outline why the term breeder is used for the reactors.

Deduce the fission reaction when ²³⁹Pu is bombarded with a neutron to produce ¹³³Xe and ¹⁰³Zr.

Nuclear disasters release radioactive caesium into the atmosphere, which presents serious health risks.

Cs-137 has a half-life of 30 years.

Calculate the percentage of Cs-137 remaining in the atmosphere after 240 years.

Deduce a Lewis (electron dot) structure of the superoxide, O₂^–, free radical.

Explain why free radicals are harmful to living cells.

Outline how a rechargeable battery differs from a primary cell.

Formulate half-equations for the reactions at the anode (negative electrode) and cathode (positive electrode) during discharge of a lithium-ion battery.

A voltaic cell consists of a nickel electrode in 1.0 mol dm⁻³ Ni²⁺ (aq) solution and a cadmium electrode in a Cd²⁺ (aq) solution of unknown concentration.

Cd (s) + Ni²⁺ (aq) → Cd²⁺ (aq) + Ni (s)               E^Θ_cell = 0.14 V

Determine the concentration of the Cd²⁺ (aq) solution if the cell voltage, E, is 0.19 V at 298 K. Use section 1 of the data booklet.

Identify the structural feature of the dye that allows the conversion of solar energy into electrical energy.

Outline the effect of sunlight on the dye in the solar cell.

State the purpose of TiO₂.

Deduce the reduction half-equation at the cathode.

Write the nuclear equation for this fission reaction.

Outline why the reaction releases energy.

The masses of the particles involved in this fission reaction are shown below.

Mass of neutron = 1.00867 amu
Mass of U-235 nucleus = 234.99346 amu
Mass of Ba-144 nucleus = 143.89223 amu
Mass of Kr-89 nucleus = 88.89788 amu

Determine the energy released, in J, when one uranium-235 nucleus undergoes fission. Use this data and information from sections 1 and 2 of the data booklet.

The critical mass for weapons-grade uranium can be as small as 15 kg. Outline what is meant by critical mass by referring to the equation in (a)(i).

The daughter product, ⁸⁹Kr, has a half-life of 3.15 min.

Calculate the time required, in minutes, for its radioactivity to fall to 10% of its initial value, using section 1 of the data booklet.

Calculate the energy released, in MeV, in this reaction, using section 36 of the data booklet.

Ethanol has a Research Octane Number (RON) of 108.6.

Outline how higher octane fuels affect engine performance.

Ethanol can be used in a direct-ethanol fuel cell (DEFC) as illustrated by the flow chart.

Deduce the half-equations occurring at electrodes A and B.

Electrode A: 

Electrode B:

State the name and function of X in the diagram in (b)(i).

Name:

Function:

Outline why aqueous ethanol, rather than pure ethanol, is used in a DEFC.

Biodiesel containing ethanol can be made from renewable resources.

Suggest one environmental disadvantage of producing biodiesel from renewable resources.

Outline how a microbial fuel cell produces an electric current from glucose.

C₆H₁₂O₆ (aq) + 6O₂ (g) → 6CO₂ (g) + 6H₂O (l)

The cell potential for the spontaneous reaction when standard magnesium and silver half-cells are connected is +3.17 V.

Determine the cell potential at 298 K when:

     [Mg²⁺] = 0.0500 mol dm⁻³
     [Ag⁺] = 0.100 mol dm⁻³

Use sections 1 and 2 of the data booklet.

Outline one difference between a primary and a secondary cell.

Calculate the relative rate of effusion of ²³⁵UF₆(g) to ²³⁸UF₆(g) using sections 1 and 6 of the data booklet.

Explain, based on molecular structure and bonding, why diffusion or centrifuging can be used for enrichment of UF₆ but not UO₂.

Deduce the half-equations for the reactions occurring at the electrodes.

Anode (negative electrode):

Cathode (positive electrode):

Calculate the cell potential, E^θ, in V, using section 24 of the data booklet.

Suggest how PEM fuel cells can be used to produce a larger voltage than that calculated in (b)(i).

Suggest an advantage of the PEM fuel cell over the lead-acid battery for use in cars.

Outline the functions of the dye, TiO₂ and the electrolyte in the operation of the DSSC.

Dye: 

TiO₂:

Electrolyte:

Suggest an advantage of the DSSC over silicon-based photovoltaic cells.

Calculate the specific energy of methane, in MJ kg⁻¹, using sections 1, 6 and 13 of the data booklet.

Calculate the maximum electric energy output, in MJ, which can be obtained from burning 1.00 kg of methane by using your answer from (a).

Hydroelectric power plants produced 16% of the world’s energy in 2015, down from 21% in 1971.

Suggest why hydroelectric power production has a higher efficiency than the other sources given in (b) and why its relative use has decreased despite the high efficiency.

Reason for higher efficiency:

Reason for decreased use:

Methane can also be obtained by fractional distillation of crude oil.

[Source: Image used with kind permission of science-resources.co.uk]

Draw a circle on the diagram to show where the methane fraction is withdrawn.

List the following products, which are also obtained by fractional distillation, according to decreasing volatility: asphalt, diesel, gasoline, lubricating motor oil.

Explain how methane absorbs infrared (IR) radiation by referring to its molecular geometry and dipole moment.

Compare methane’s atmospheric abundance and greenhouse effect to that of carbon dioxide.

Some solar cells use photovoltaic semi-conductors. Compare, giving reasons, the electrical conductivity of metals and semi-conductors as temperature increases.

Suggest one advantage of a dye-sensitized solar cell (DSSC) over a silicon based photovoltaic cell.

Determine the other product of the fission reaction of plutonium-239.

$${}_{94}^{239}\text{Pu + }{}_0^1\text{n}\to {}_{54}^{134}\text{Xe + }.................{\text{ + 3}}_0^1\text{n}$$

Outline the concept of critical mass with respect to fission reactions.

Outline one advantage of allowing all countries access to the technology to generate electricity by nuclear fission.

State one advantage of using fusion reactions rather than fission to generate electrical power.

Outline how the energy of a fission reaction can be calculated.

Calculate the half-life of an isotope whose mass falls from 5.0 × 10⁻⁵ g to 4.0 × 10⁻⁵ g in 31.4 s, using section 1 of the data booklet.

The regular rise and fall of sea levels, known as tides, can be used to generate energy.

State one advantage, other than limiting greenhouse gas emissions, and one disadvantage of tidal power.

Advantage:

Disadvantage:

Deduce the half-equations and the overall equation for the reactions taking place in a direct methanol fuel cell (DMFC) under acidic conditions.

Outline one advantage and one disadvantage of the methanol cell (DMFC) compared with a hydrogen-oxygen fuel cell.

State the nuclear equation for the fusion reaction.

Explain why fusion is an exothermic process.

Calculate the heat energy released, in J, by the fusion reaction producing one atom of carbon-12. Use section 2 of the data booklet and E = mc².

Beryllium-8 is a radioactive isotope with a half-life of 6.70 × 10⁻¹⁷ s.

Calculate the mass of beryllium-8 remaining after 2.01 × 10⁻¹⁶ s from a sample initially containing 4.00 g of beryllium-8.

Crude oil can be converted into fuels by fractional distillation and cracking.

Contrast these two processes.

Determine the specific energy, in kJ g⁻¹, and energy density, in kJ cm⁻³, of hexane, C₆H₁₄. Give both answers to three significant figures.

Hexane: M_r = 86.2; ΔH_c = −4163 kJ mol⁻¹; density = 0.660 g cm⁻³

Specific energy:

Energy density:

Hydrocarbons need treatment to increase their octane number to prevent pre-ignition (knocking) before they can be used in internal combustion engines.

Describe how this is carried out and the molecular changes that take place.

Sketch graphs to show the general effect of increasing temperature on the electrical conductivity of semiconductors and metals on the axes below.

Explain the function of dyes in a dye-sensitized solar cell (DSSC).

This question is about biofuel.

Evaluate the use of biodiesel in place of diesel from crude oil.

Discuss the data.

Outline what is meant by the degradation of energy.