NEW AQA AS LEVEL STARTING SEPTEMBER 2008
PRACTICE PAPER 3
The questions for this paper are taken from January 2008 Unit 1 and Unit 3 AQA past papers as follows:
1 Jan 08 Unit 1 Q1
7
8
2
3
4
5
6 a
6 b
Jan 08 Unit 1 Q2
Jan 08 Unit 1 Q3 a - d
Jan 08 Unit 3 Q1
Jan 08 Unit 3 Q2 a - d
Jan 08 Unit 3 Q4a
Jan 08 Unit 3 Q4c
Jan 08 Unit 1 Q5
Jan 08 Unit 1 Q6
Please consult the relevant sections of the Jan 08 Unit 1 and Unit 3 mark schemes for the answers and mark schemes for these questions.
THE TOTAL MARKS AVAILABLE FOR THIS PAPER IS
71
TIME ALLOWED: 1 HOUR 15 MINUTES

1 Relative atomic mass can be determined using a mass spectrometer
(a) Define the term relative atomic mass .
.........................................................................................................................................
.........................................................................................................................................
(b) To obtain a mass spectrum of an element, a gaseous sample of that element must first be ionised. The ions produced are then accelerated, deflected and detected.
(2 marks)
(i) State what is used to accelerate ions in a mass spectrometer.
.............................................................................................................................
(ii) State what is used to deflect ions in a mass spectrometer.
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(iii) Explain how ions are detected in a mass spectrometer
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(3 marks)

c) A sample of chlorine was placed in a mass spectrometer. In this sample of chlorine, 75 % of the atoms were
35
Cl atoms and 25 % were
37
Cl atoms.
The mass spectrometer detected only Cl
+
ions and Cl
2+
ions. The spectrum only contained four peaks. The diagram below shows an incomplete spectrum, showing only the peak produced by the 35 Cl + ions.
0 10 20 30 40
(i) Label both axes on the diagram.
(ii) Complete this diagram to show the remaining three peaks in the mass spectrum of the chlorine sample.
(5 marks)
/10

2 Sodium carbonate neutralises hydrochloric acid as shown in the equation below:
Na
2
CO
3
+ 2HCl

2NaCl + CO
2
+ H
2
O
(a) Sodium carbonate is used to neutralise a 100 cm
3
sample of 1.75 moldm
-3 hydrochloric aid.
(i) Calculate the number of moles of HCl in the 100 cm
3
sample of 1.75 moldm
-3 hydrochloric acid.
.............................................................................................................................
(ii) Deduce the number of moles, and hence the mass, of Na
2
CO
3
(M r
= 106.0) required to neutralise this sample of hydrochloric acid.
Moles of Na
2
CO
3
.................................................................................................
Mass of Na
2
CO
3
...................................................................................................
.............................................................................................................................
(3 marks)
(b) Hydrated sodium carbonate has the formula Na
2
CO
3
.10H
2
O.
(i) Calculate the percentage, by mass, of Na
2
CO
3
in hydrated sodium carbonate.
.............................................................................................................................
.............................................................................................................................
.............................................................................................................................
(ii) Calculate the mass of hydrated sodium carbonate required to neutralise 0.267 mol of hydrochloric acid.
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(4 marks)

(c) A sample of sodium carbonate reacted to produce 7.75 x 10 mol
-2
of CO
2
.
State the ideal gas equation and use it to calculate the volume of CO
2
produced, at
298 K and 101 kPa, in this reaction.
Ideal gas equation ………………………...…………………………………………...
Volume of CO
2
produced ................................................................................................
…..................................................................................................................................
…..................................................................................................................................
…..................................................................................................................................
…..................................................................................................................................
(4 marks)
/11

3 (a) A period 3 element, E , forms an ion E
2-
which has the electron arrangement shown below:
1s 2 2s 2 2p 6 3s 2 3p 6
Give the electron arrangement of an atom of element E and identify this element.
Electron arrangement of an atom of E ...........................................................................
Identity of E ....................................................................................................................
(2 marks)
(b) There is a trend in electronegativity of the Period 3 elements Na to Cl.
(i) Define the term electronegativity.
.............................................................................................................................
.............................................................................................................................
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(ii) State and explain the trend in the electronegativity of the Period 3 elements
Na to Al.
Trend ..................................................................................................................
Explanation .......................................................................................................
.............................................................................................................................
.............................................................................................................................
(5 marks)
(c) Some electronegativity values are given below:
Electronegativity value
H
2.1
F
4.0
Cl
3.0
Br
2.8
I
2.5
(i) Explain why the covalent bond in HF is polar.
.............................................................................................................................
.............................................................................................................................

(ii) State and explain the trend in polarity of the covalent bonds in the hydrogen halides HF, HCl, HBr and HI.
Trend ..................................................................................................................
Explanation ........................................................................................................
.............................................................................................................................
.............................................................................................................................
(3marks)
(d) The boiling points of some hydrogen halides are shown in the table below:
Hydrogen Halide
Boiling Point / K
HF
293
HCl
188
HBr
206
HI
238
Explain, in terms of the intermolecular forces present, why
(i) the boiling point of HF is much higher than those of the other hydrogen halides.
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(ii) the boiling points increase from HCl to HI
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(6 marks)
/16

4 Petroleum and natural gas are mixtures of alkanes with sulphur-containing impurities.
Alkanes are saturated hydrocarbons.
(a) (i) Name the process that is used to separate petroleum into useful fractions.
.............................................................................................................................
(ii) State what is meant by the term petroleum fraction .
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(2 marks)
(b) State what is meant by the term saturated hydrocarbon.
.........................................................................................................................................
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(1 mark)
(c) Pollutants are formed when hydrocarbon fractions are burned in a limited supply of air.
(i) Write an equation for the incomplete combustion of decane (C
10
H
22
) to give carbon monoxide and water only.
.............................................................................................................................
(ii) Identify a solid pollutant which could form during the incomplete combustion of decane.
.............................................................................................................................
(iii) Identify the pollutant which would be formed from the sulphur-containing impurities in petroleum if they were burned.
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(3 marks)

5
(d) When they are burned in air, the alcohols methanol and ethanol produce smaller amounts of pollutants than petroleum fractions.
(i) Write an equation for the complete combustion of methanol, CH
3
OH.
.............................................................................................................................
(ii) It may be desirable to increase the use of ethanol as a fuel in the future.
Give one reason for this, other than the production of smaller amounts of pollutants.
.............................................................................................................................
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(2 marks)
/8
The first four members of the homologous series of alkenes are shown below: ethane propene
H
2
C=CH
2
H
2
C=CHCH
3 but-1-ene H
2
C=CHCH
2
CH
3 pent-1-ene H
2
C=CHCH
2
CH
2
CH
3
(a) One characteristic of an homologous series is that it can be represented by a general formula.
(i) Give the general formula for these alkenes.
.............................................................................................................................
(ii) State two other characteristics of an homologous series.
Characteristic 1 ..................................................................................................
.............................................................................................................................
Characteristic 2
………………………………………………………………..
.............................................................................................................................
(3 marks)
(b) Give the molecular formula for the next member of this homologous series.
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(1 mark)

6
(c) Draw the structure of the position isomer of pent-1-ene.
.........................................................................................................................................
(1 mark)
(d) Buta-1,3-diene has the formula
H
2
C=CH-CH=CH
2
(i) State what is meant by the term empirical formula .
.............................................................................................................................
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(ii) Give the empirical formula of buta-1,3-diene
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(2 marks)
/7
Catalysts are used extensively in reactions.
(a) Write an equation for the reaction between nitrogen monoxide and carbon monoxide in a catalytic converter of a petrol-engined car. Identify a catalyst used in a catalytic converter.
Equation ……………………………………………………………………………….
Catalyst ………………………………………………………………………………...
(2 marks)
(b) Write an equation for the catalytic cracking of dodecane (C
12
H
26
) to form cyclohexane and one other alkane. Identify the catalyst used in this reaction.
Equation ……………………………………………………………………………….
Catalyst ………………………………………………………………………………...
(2 marks)
/4

7
8
(a) Explain why the shape of the NH
4
+
ion is regular tetrahedral. Explain why the bond angle in the NH
3
molecule is less than that in the NH
4
+ ion.
(4 marks)
(b) Draw the shape, including any lone pairs of electrons, of the NH
2
ion. Name the shape produced by the arrangement of atoms in the NH
2
-
ion.
(2 marks)
(a) Explain, in terms of its structure and bonding, why the melting point of silicon is very high.
(4 marks)
(b) Select any two of the Period 3 elements phosphorus, sulphur and chlorine. State and explain which of your selected elements has the higher melting point.
(5 marks)