State one advantage and one disadvantage for each energy source in the table.

Calculate the specific energy of hydrogen, stating its units. Refer to sections 1, 6 and 13 of the data booklet.

Hydrogen has a higher specific energy than petrol (gasoline) but is not used as a primary fuel source in cars. Discuss the disadvantages of using hydrogen.

Do not award marks for converse statements for advantage and disadvantage.

Points related to greenhouse gases should be counted only once for the entire question.

Biofuels:

Accept “«close to» carbon neutral”, “produce less greenhouse gases/CO₂” as an advantage.

Accept “engines have to be modified if biodiesel used” as a disadvantage.

Fossil Fuels:

Accept specific pollution examples (eg, oil spills, toxic substances released when burning crude oil, etc.) as a disadvantage.

[4 marks]

«specific energy =» 142

kJ\(\,\)g^–1

Accept other correct values with the correct corresponding units.

M2 can be scored independently.

[2 marks]

large volumes of hydrogen required
OR
hydrogen has lower energy density

not easily transportable «form» as it is a gas
OR
heavy containers required to carry AND compress/regulate «hydrogen»
OR
high energy/cost required to compress hydrogen to transportable liquid form
OR
atmospheric pollution may be generated during production of hydrogen
OR
hydrogen fuel cells do not work at very low temperatures
OR
highly flammable when compressed/difficult to extinguish fires
OR
leaks not easy to detect
OR
high cost of production
OR
lack of filling stations/availability to consumer «in many countries»

Accept “«hydrogen combustion contributes to» knocking in engines” OR “modified engine required” for M2.

Accept “explosive” but not “more dangerous” for M2.

[2 marks]