IB Chemistry HL 1.3 Energy from Fuels Question Bank

Practise IB Chemistry HL 1.3 with SL and HL questions on combustion, fuel comparisons, biofuels and fuel-cell equations linked to energy transfer.

Covered syllabus points

1.3.1—Combustion reactions 1.3.2—Incomplete combustion 1.3.3—Fossil fuels 1.3.4—Biofuels 1.3.5—Fuel cells 1.4.1 (HL)—Entropy (S)1.4.2 (HL)—Gibbs energy (ΔG)1.4.3 (HL)—Spontaneity 1.4.4 (HL)—Equilibrium and Gibbs energy

[Maximum number: 2]

Urea, $\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}$ , is excreted by mammals and can be used as a fertilizer.

The combustion of urea produces water, carbon dioxide and nitrogen.

Formulate a balanced equation for the reaction.

$2\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}(\mathrm{~s})+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 4 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+2 \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{~N}_{2}(\mathrm{~g})$

correct coefficients on LHS

correct coefficients on RHS

$\text { Accept }\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}(\mathrm{~s})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow$

Marking guidance:

Accept any correct ratio.

[Maximum number: 1]

Ethanol is obtained by the hydration of ethene, $\mathrm{C}_{2} \mathrm{H}_{4}$ .

Suggest two possible products of the incomplete combustion of ethene that would not be formed by complete combustion.

[Maximum number: 5]

Ethanol is a biofuel that can be mixed with gasoline.

(a)

Write the equation for the complete combustion of ethanol.

[ 1 ]

$\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l})+3 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

(b)

Outline the evidence that relates global warming to increasing concentrations of greenhouse gases in the atmosphere.

[ 2 ]

Any two of:

«showing strong» correlation between «atmospheric» $\ce{CO2}$ concentration/greenhouse gas concentration and average «global/surface/ocean» temperature

lab evidence that greenhouse gases/ $\mathrm{CO}_{2}$ absorb(s) infrared radiation «advanced» computer modelling

ice core data

tree ring data

ocean sediments / coral reefs / sedimentary rocks data

Marking guidance:

Do not accept "global warming" for "average temperature".

Do not accept "traps/reflects heat" OR "thermal energy".

Evidence must be outlined and connected to data.

Accept references to other valid greenhouse gases other than carbon dioxide/ $\mathrm{CO}_{2}$ , such as methane/ $\mathrm{CH}_{4}$ or nitrous oxide/ $\mathrm{N}_{2} \mathrm{O}$ .

2 max

(c)

Explain, including a suitable equation, why biofuels are considered to be carbon neutral.

[ 2 ]

biofuel raw material/sugar/glucose formed by photosynthesis

OR

biofuel raw material/sugar/glucose uses up carbon dioxide during its formation OR

biofuel from capturing gases due to decaying organic matter formed from photosynthesis

$6 \mathrm{CO}_{2}(\mathrm{~g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{aq})+6 \mathrm{O}_{2}(\mathrm{~g})$

Marking guidance:

Accept arguments based on material
coming from plant sources consuming
carbon dioxide/carbon for M1.

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Covered syllabus points

1.3 Energy from fuels question 1

1.3 Energy from fuels question 2

1.3 Energy from fuels question 3

Question (a)

Question (b)

Question (c)