Chemistry

Topics: Petroleum, Gasoline, Alkane Pages: 11 (2885 words) Published: October 7, 2014
1.(a)The diagram below represents the industrial fractional distillation of crude oil.

(i)Identify fraction A.
(ii)What property of the fractions allows them to be separated in the column? (2)
(b)A gas oil fraction from the distillation of crude oil contains hydrocarbons in the C15 to C19 range. These hydrocarbons can be cracked by strong heating. (i)Write the molecular formula for the alkane with 19 carbon atoms. (ii)Name the type of reaction involved in cracking.

(iii)Write an equation for one possible cracking reaction of the alkane C16H34 when the products include ethene and propene in the molar ratio 2:1 and only one other compound. (4)
(Total 6 marks)
2.A compound of carbon, hydrogen and nitrogen contains 61.0% of carbon and 15.3% of hydrogen by mass. (i)Calculate the empirical formula of the compound.
(ii)What other piece of data is required to deduce the molecular formula from the empirical formula? (iii)If the molecular formula of the compound is the same as the empirical formula, draw two possible structures of the compound. (Total 6 marks)

3.(a)Compound A (Mr = 215.8) contains 22.24% carbon, 3.71% hydrogen and 74.05% bromine by mass. Show that the molecular formula of A is C4H8Br2. (3)
(b)There are nine structural isomers of molecular formula C4H8Br2, three of which have branched carbon chains. Give the names and draw the displayed formulae for any two of the branched chain isomers of C4H8Br2. (4)

(Total 8 marks)
4.The table below shows the fractions obtained from crude oil. Name of fraction
Number of
carbon atoms
Use
Gases
1-4
bottled fuels for camping
Petrol (gasoline)
4-12
fuel for cars
Naphtha
7-14

11-15
jet fuel
Gas oil (diesel)
15-19
central heating fuel
Mineral oil
20-30
lubrication
Fuel oil
30-40

Wax
41-50
candles
Bitumen
over 50
road surfacing

(a)Complete the table above by writing in the empty boxes
(3)
(b)Give one structural formula in each case for the following components of crude oil: (i)the isomer of C5H12 with the lowest boiling point
(ii)a saturated compound with molecular formula C5H10
(2)
(c)Give a molecular formula for each of the following components of crude oil: (i)the alkane which, on cracking, forms, as the only products, two moles of ethene and one mole of butane per mole of alkane.

(ii)the straight chain alkane found in the petrol fraction which contains the lowest percentage by mass of hydrogen. Refer to the table at the start of the question to deduce your answer. (2)
(d)Write an equation for the complete combustion of the alkane which requires 11 moles of oxygen per mole of alkane for complete combustion. (2)
(Total 9 marks)
5.There are eight structural isomers with the molecular formula C5H11Br. Four of these are classed as primary, three as secondary and one as tertiary. The graphical formula of one of the secondary compounds, isomer A, is shown below.

isomer A

(i)Give the name of isomer A.
(2)
(ii)Explain what is meant by the term structural isomers.
(2)
(iii)Draw the graphical formula of the tertiary compound with molecular formula C5H11Br, isomer B. (1)
(Total 5 marks)
6.(a)Central heating fuel is obtained by distillation of crude oil. An alkane present in central heating fuel contains 16 carbon atoms per molecule. When a molecule of this alkane is cracked, propene is formed. (i)Name the crude oil fraction used as central heating fuel. (ii)Write an equation for the cracking of the 16-carbon alkane to form octane, propene and ethene as the only products. (iii)Give one important commercial use of propene.

(4)
(b)A catalytic converter in the exhaust system of a car contains a ceramic honeycomb covered with a thin coating of the catalyst. When hot gases containing nitrogen monoxide and unburnt octane are passed over the catalyst, they react to form nitrogen, carbon dioxide and water. (i)Explain why the catalyst is coated on a honeycomb.

(ii)...
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