A-Level Chemistry Question and Answers 2015 · PDF file6 Atomic Structure (Answers) Answer outline and marking scheme for question: 1 a) Particle Relative Charge Relative Mass Electron

A-Level Chemistry Question and Answers 2015

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Table of Contents Topics that only contain interactive questions ................................................................................. 3
Atomic Structure (Questions) * .......................................................................................................... 4
Atomic Structure (Answers) ................................................................................................................ 6
Atoms, Molecules and Stoichiometry (Questions) ........................................................................... 8
Atoms, Molecules and Stoichiometry (Answers) .............................................................................. 9
Chemical Equilibria (Questions) ........................................................................................................ 11
Chemical Equilibria (Answers) .......................................................................................................... 12
Electrochemistry (Questions) * ........................................................................................................ 13
Electrochemistry (Answers)............................................................................................................... 14
Group II and Group IV (Questions) * .............................................................................................. 15
Group II and Group IV (Answers) .................................................................................................... 16
Group VII (Questions)........................................................................................................................ 18
Group VII (Answers) .......................................................................................................................... 19
Ionic Equilibria (Questions) ............................................................................................................... 20
Ionic Equilibria (Answers) .................................................................................................................. 22
Reaction Kinetics (Questions) ........................................................................................................... 24
Reaction Kinetics (Answers) .............................................................................................................. 25
States of Matter (Questions) ............................................................................................................. 26
States of Matter (Answers) ............................................................................................................... 27
* = topics that contain interactive resources, multiple choice questions or audio files. To interact
with this content, please go to www.s-cool.co.uk/a-level/chemistry. These questions cover the main areas of this subject. Please check the specific areas you need with your exam board. They are provided as is and S-cool do not guaranteed the suitability, accuracy or completeness of this content and S-cool will not be liable for any losses you may incur as a result of your use or non-use of this content. By using these notes, you are accepting the standard terms and
conditions of S-cool, as stated in the s-cool website (www.s-cool.co.uk).
http://www.s-cool.co.uk/a-level/chemistryhttp://www.s-cool.co.uk/

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Topics that only contain interactive questions
These topics only contain interactive questions such as animations, multiple choice or audio files. To
interact with this content, please go to www.s-cool.co.uk/biology.
Aliphatic Compounds
Aromatic and Plastics
Chemical Energetics
General Principles
Ionic Equilibria
Periodicity
Transition Metals

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Atomic Structure (Questions) *
1. Chemists use a model of an atom that consists of three types of sub-atomic particle. These are protons,
neutrons and electrons.
a) Complete the table below, which shows the properties of these particles.
Particle Relative Charge Relative Mass
Electron
Proton
1
Neutron 0
(4 marks)
b) Types of atoms and ions vary from each other by the number of sub-atomic
particle found in them. What differences are there between 12C and
14C?
(1 mark)
c) Define the term 'isotope'.
(1 mark)
d) Write down the electronic configuration of Cr3+.
(1 mark)
(Marks available: 7)
2.
a) The first ionisation energy for lithium is 519 kJmol-1.
Write an equation to show what is meant by this statement.
(1 mark)

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b) The second ionisation energy for lithium is 7300 kJmol-1.
Explain the difference in value for the first and second ionisation energy for
lithium.
(1 mark)

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Atomic Structure (Answers)
Answer outline and marking scheme for question: 1
a)
Particle Relative Charge Relative Mass
Electron -1 1/1820 or negligible
Proton +1 1
Neutron 0 1
(4 marks)
b) 12C has 6 protons, 6 neutrons and 6 electrons. 14C
has 6 protons, 6 electrons and 8 neutrons. The difference between this pair
is that 14C has two more neutrons than 12C.
(1 mark)
c) An isotope of an element has the same number of protons but a different
number of neutrons.
(1 mark)
d) 1s2 2s2 2p6 3s2 3p6
3d3 4s0
(1 mark)

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a) Li(g) - e- = Li+(g)
The electronic configuration of lithium is 1s2 2s1. It
is relatively easy to remove the electron from the 2s orbital as it is shielded
from the nuclear charge by the 1s electrons.
(1 mark)
b) To remove the second electron for the second ionisation energy requires
considerably more energy as this electron comes from the 1s shell which is closer
to the nucleus and not subject to any shielding.
(1 mark)

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Atoms, Molecules and Stoichiometry (Questions)
1. Calculate the mean relative atomic mass of nickel from the mass spectrum.
2. In 1774 Joseph Priestly conducted one of his most famous experiments which
lead to a method for the preparation of oxygen. The experiment involved heating
a sample of mercury II oxide with a large lens.
The equation for this reaction is shown below:
2HgO(s) = 2Hg(l) + O2(g)
a) What volume of O2(g) would be obtained if 1.08g of mercury
II oxide were completely decomposed? (Given that 1 mole of a gas occupies 24
dm3 under the experimental conditions)
3. An organic compound is found to have the following composition by mass:
C 72.7%; H 6.1%; N 21.2%.
a) Calculate the empirical formula of the compound.
(2 marks)
b) The molar mass of the compound is 198 gmol-1. Calculate
the molecular formula of the compound.
(3 marks)

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Atoms, Molecules and Stoichiometry (Answers)
Intensities of peaks:
58Ni = 10.2 = 69.4% of total (abundance)
(Sum of intensities = 14.7)
Mean relative atomic mass = (58 x 69.4) + (59 x 26.5) + (62 x 4.1) =
58.4
100
Molar mass of HgO = 201 + 16 = 217 gmol-1
1.08g of HgO will contain 1.08 / 217 mols = 0.005mol
From the equation, 1 mole of O2(g) is produced from 2 moles of HgO
This means that 0.005 mol of HgO will produce 0.005 / 2 mol of O2 = 0.0025 mol
0.0025 mol of O2 will occupy 0.0025 x 24dm3 = 0.06dm3

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Ratio of elements in compound C : H : N
Ratio C : N : H = 72.7 / 12 : 6.1 / 1 : 21.2 / 14 = 6.1 : 6.1 : 1.5
Whole number ratio = 4 : 4 : 1
Empirical formula of compound is C4H4N

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Chemical Equilibria (Questions)
1.
Esters are a useful group of compounds due to their distinctive smells. One example
of an ester is ethyl ethanoate, its formation is shown below.
CH3COOH(aq) + C2H5OH(aq)CH3COO C2H5(aq)
+ H2O(l)
a) Systems like this are described as being a 'dynamic equilibrium'. Explain
the term 'dynamic equilibrium'
b) Write down the expression for the equilibrium constant, Kc, for this reaction.
c) Calculate the value of Kc for this reaction given the equilibrium concentrations below.
[CH3COOH] = 0.08 moldm-3
[C2H5OH] = 0.08 moldm-3
[CH3COO C2H5] = 0.25 moldm-3
[H2O] = 0.1 moldm-3
d) Concentrated sulphuric acid is added to the reaction mixture as it removes water molecules. What effect
would this have on the equilibrium position of this system?
2. The Haber-Bosch process is used for the large-scale production of ammonia from
nitrogen and hydrogen gas. The reaction is shown below:
N2(g) + 3H2(g)2NH3(g)
a) Write an expression for Kp for this reaction.
b) What are the units of Kp for this reaction? (Assume pressure is me

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A-Level Chemistry Question and Answers 2015 · PDF file6 Atomic Structure (Answers) Answer outline and marking scheme for question: 1 a) Particle Relative Charge Relative Mass Electron