Question 18M.3.sl.TZ2.10
| Date | May 2018 | Marks available | [Maximum mark: 6] | Reference code | 18M.3.sl.TZ2.10 |
| Level | sl | Paper | 3 | Time zone | TZ2 |
| Command term | Formulate, Identify, Justify, Outline | Question number | 10 | Adapted from | N/A |
Crude oil is a useful energy resource.
Outline two reasons why oil is one of the world’s significant energy sources.
[2]
Any two of:
high energy content/high energy density/high specific energy
OR
high enthalpy of combustion/very exothermic enthalpy of combustion
shortage of alternatives
OR
alternatives are expensive
OR
oil is relatively cheap
OR
oil is «still» abundant/common
well-established technology
OR
easy for consumers to obtain
OR
commonly used
easy to store
OR
easy to transport
OR
easy to extract
produces energy at a reasonable rate
Accept “high potential energy” for M1.
[2 marks]
Formulate an equation for the cracking of C16H34 into two products with eight carbon atoms each.
[1]
C16H34(g) → C8H16(g) + C8H18(g)
OR
C16H34(g) + H2(g) → 2 C8H18(g)
[1 mark]
Identify, giving a reason, which product in (b)(i) could be used in petrol (gasoline).
[1]
C8H18 AND is an alkane
OR
C8H18 AND petrol does not contain alkenes
[1 mark]
Outline how higher octane fuels help eliminate “knocking” in engines.
[1]
fuels can be compressed more without undergoing «unwanted» auto-ignition
Accept “burns smoother without undergoing «unwanted» auto-ignition” OR “fuel does not auto-ignite”.
[1 mark]
The performance of hydrocarbons as fuels can be improved by catalytic reforming.
Outline how catalytic reforming increases a fuel’s octane rating.
[1]
produces more branched chain hydrocarbons «with higher octane rating»
OR
produces aromatics «which have higher octane rating»
OR
produces cyclohexanes «which have higher octane rating»
Accept “increase branches”.
Do not accept “produces benzene”.
Do not penalize for “benzene” if penalty applied in 2.b.iii.
Accept “produces cyclic structures”.
[1 mark]