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Date November 2016 Marks available 2 Reference code 16N.3.sl.TZ0.11
Level SL Paper 3 Time zone TZ0
Command term Calculate and Suggest Question number 11 Adapted from N/A

Question

Chemical energy from redox reactions can be used as a portable source of electrical energy. A hybrid car uses a lithium ion battery in addition to gasoline as fuel.

(i) Calculate the specific energy of the lithium ion battery, in MJ kg−1, when 80.0 kg of fuel in the battery releases 1.58 × 107 J. Use section 1 of the data booklet.

(ii) The specific energy of gasoline is 46.0 MJ kg−1. Suggest why gasoline may be considered a better energy source than the lithium ion battery based on your answer to part (a) (i).

[2]
a.

(i) The energy density of gasoline is 34.3 MJ dm−3. Calculate the volume of gasoline, in dm3, that is equivalent to the energy in 80.0 kg of fuel in the lithium ion battery. Use section 1 of the data booklet.

(ii) The efficiency of energy transfer by this lithium ion battery is four times greater than that of gasoline. Determine the distance, in km, the car can travel on the lithium ion battery power alone if the gasoline-powered car uses 1.00 dm3 gasoline to travel 32.0 km.

[2]
b.

Markscheme

i
«\(\frac{{1.58 \times {{10}^7}{\rm{J}}}}{{80.0{\rm{kg}}}}\)=\(\frac{{15.8{\rm{MJ}}}}{{80.0{\rm{kg}}}}\)=» 1.98 × 10−1 «MJ kg−1»

ii
gasoline releases more energy from a given mass of fuel
OR
gasoline has higher specific energy
Do not accept volume in place of mass as question refers to specific energy, not energy density.

a.

i
«\(\frac{{15.8\,{\text{MJ}}}}{{34.3\,{\text{MJ}}\,{\text{d}}{{\text{m}}^{ - 3}}}}\)»= 4.61 × 10−1 «dm3»

ii
«4.61 × 10−1 dm× 32.0 km dm−3 × 4»= 59.0/59.1 «km»

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Options » C: Energy » C.1 Energy sources

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