IB Chemistry HL 1.3 Energy From Fuels Questions

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

Exam points

Balance complete and incomplete combustion equations for hydrocarbons and alcohols, identifying carbon monoxide and soot products.
Compare fossil and biofuels using carbon dioxide output, energy yield and renewable carbon-cycle evidence.
Write fuel-cell half-equations and relate chemical energy conversion to electrical output.

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

Learn this topic

Study 1.3 Energy from fuels conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

[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.

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

[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.

All question bank results loaded

Covered syllabus points

Learn this topic

Question 1

Question 2

Question 3

Question (a)

Question (b)

Question (c)