SHREWSBURY SCHOOL
SIXTH FORM ENTRANCE
EXAMINATION 2009
CHEMISTRY
(1 hour)
Instructions to candidates:
 Answer THREE questions from SECTION A and THREE questions
from SECTION B.
 Each question is worth 10 marks.
 Answer on lined paper.
 You may use a calculator.
 You are provided with a copy of the periodic table.
Section A. Answer 3 questions only from this section.
1.
John Dalton was a famous chemist who died 200 years ago. He made a list of
substances that he thought were elements and gave them symbols. Here is a
copy of his table.
a)
We know some substances (such as hydrogen, carbon, oxygen, silver, gold and
copper) are elements. Write down the names of two other substances that we
know are elements.
[1]
b)
Dalton stated that all elements are made up of atoms that cannot be split up into
simpler particles. We now know that atoms contain smaller particles. Describe,
with the aid of a labelled diagram, the structure of an atom of lithium. Use of the
Periodic table may be helpful.
[3]
c)
The element, lithium, has two different natural occurring atoms: lithium-6 and
lithium-7. These are called isotopes. Define the term ‘isotope’.
[2]
d)
Lithium is a reactive Group 1 element. Lithium is an example of a substance with
what type of bonding between its particles?
[1]
e)
Lithium reacts readily in the presence of oxygen to form lithium oxide (Li2O). Write
a balanced symbol equation for this reaction.
[1]
f)
Lithium also reacts vigorously with cold water. Suggest one main observation you
would see if you performed this experiment in a laboratory and write a word
equation for the reaction that occurs.
[2]
2.
This question is about organic chemistry (the study of carbon containing
compounds). This question focuses on two organic molecules, chloroethene and
chloroethane.
Chloroethene
Chloroethane
a)
Name the raw material from which most organic compounds are obtained
from.
[1]
b)
Write down the molecular formula of chloroethene and chloroethane.
[1]
c)
Chloroethene is a member of the alkene family, whereas chloroethane is an alkane.
Describe the chemical test you would use to distinguish between this alkene and
alkane. Give the expected result for both chloroethene and chloroethane.
[2]
d)
Chloroethene can be used to make the polymer, poly(chloroethene), which is used
to make water pipes.
(i)
What is the important feature of the structure of chloroethene which allows it to act
as a monomer for this polymerisation reaction?
[1]
(ii)
Draw a section of poly(chloropropene) showing two repeating units of the polymer.
[2]
e)
Poly(chloroethene) is classified as a non-biodegradable polymer. What does the
term ‘non-biodegradable’ mean? Name one suitable method of disposing of this
polymer, other than landfill.
[2]
f)
Another useful polymer in the home is poly(tetrafluoroethene). This is more
commonly known as Teflon and it is used as a non-stick coating on cookware. Draw
the structure of the monomer of this polymer.
[1]
3.
This question is about chemical bonding. The table shows some information about
some compounds.
Formula
Type of structure
Melting point in oC
CaO (calcium oxide)
Giant
2900
H2O (water)
Molecular
0
NaF (sodium fluoride)
Giant
933
NH3 (ammonia)
Molecular
-78
a)
What is the trend between the melting point and the type of structure? Use the
information in the table to help you.
[2]
b)
The structure of a water molecule compound can be represented like this:
Water
The atoms are held together by covalent bonds. Define the term covalent bonding.
[1]
c)
Ammonia is also a covalent molecule. Draw the dot and cross diagram to show the
arrangement of electrons in a molecule of ammonia.
You need only show electrons in outer shells.
[2]
d)
The melting point of calcium oxide is 2900oC. Explain why the melting point of
calcium oxide is so high.
[2]
e)
Calculate the relative formula mass of calcium oxide, CaO.
Use the Periodic Table to help you.
[1]
f)
Calcium oxide readily reacts with water to form a solution of calcium hydroxide,
Ca(OH)2. Suggest an approximate value of the pH of this solution.
[1]
g)
Sodium fluoride, NaF, can be prepared by direct combination of its elements, sodium
and fluorine. Write a balanced symbol equation for this reaction.
[1]
4.
This question involves a simple chemical reaction and the questions that follow are all
to do with the quantities of substance involved in the reaction. Show full working.
The simplest method of making magnesium oxide is to directly react magnesium and oxygen
together:
2Mg + O2  2MgO
Relative atomic mass (Ar) of magnesium = 24, and Ar of oxygen = 16.
a)
Name one safety precaution you would need to take when carrying out this reaction
(assume lab coats and goggles are already being worn).
[1]
b)
1.2 grams of magnesium were burned in excess oxygen.
(i)
What does the word ‘excess’ mean?
[1]
(ii)
What mass of magnesium oxide would we expect to form?
[2]
(iii)
In the experiment, only 1.4 grams of magnesium oxide were formed. What is the
percentage yield of this reaction?
[1]
c)
Another magnesium compound, magnesium nitride, Mg3N2 was formed when doing
this experiment.
(i)
Write a balanced symbol equation for the formation of this product.
[2]
(ii)
What is the charge on the nitride, N, ion?
[1]
d)
In another reaction, 1.2 grams of calcium were burned in excess oxygen and formed
calcium oxide, CaO. What mass of calcium oxide would you expect to form? [2]
Section B. Answer 3 questions only from this section.
5.
This question is about fuels. Sulfur compounds are found in fuels from crude oil.
Pollution is caused when these sulfur compounds are burned. The EU has made it a
requirement that the amount of sulfur allowed in road fuels will be limited to 10 ppm
from 2009.
a)
(i)
Identify the sulfur compound formed when petrol burns.
(ii)
This sulfur compound formed in (i) is bad for the environment. Explain why.
[2]
[1]
b)
What is the name of the separation process in which petrol is obtained from crude
oil?
[1]
c)
(i)
Petrol consists of a some hydrocarbons with the formula, C5H12.
structural formulae of two different compounds with this formula.
Draw
[2]
d)
Ethanol (C2H5OH) is being used as a additive to petrol to conserve fossil fuels in
some countries like Brazil and Italy. Write a balanced symbol equation for the
complete combustion of ethanol.
[2]
e)
Incomplete combustion of hydrocarbon fuels results in the formation of a poisonous
gas. Identify this gas.
[1]
f)
Combustion is an exothermic reaction.
exothermic reaction.
Give another example of a type of
[1]
6.
The question is about metals and their reactions.
Iron is a transition metal that is extracted from iron (III)oxide, Fe2O3, using carbon in
a blast furnace. Copper is also a transition metal that can be extracted by this
method.
a)
Name two other elements that are transition metals.
Use of your Periodic Table may be helpful.
b)
[1]
State the number of protons, neutrons and electrons in an atom of iron.
[2]
c)
Write a balanced symbol equation for the reaction that takes place between iron(III)
oxide and carbon in the blast furnace.
[2]
d)
The iron formed in this process is known as cast iron, which is a brittle and corrodes
very easily. Most of this iron is converted into pure iron then mixed with other
elements to form an alloy.
Show, with the aid of a diagram, the main differences in the structure of a pure metal
and an alloy and how this affects the malleability of the material.
[2]
e)
Alumumium is extracted by electrolysis. Impure copper obtained from a similar
method using a blast furnace can be purified by electrolysis. The purified copper is
used in electrical wiring in houses.
What are the main physical properties of copper that make it suitable for this
purpose
[2]
f)
Aluminium can not be extracted by this method. Suggest a suitable reason why.
[1]
7. This question is about acids.
Asborbic acid (Vitamin C) is an essential nutrient for humans. There are many other
naturally occurring molecules like citric acid (in citrus fruits) and tartaric acid (in grapes and
bananas).
a)
Asborbic acid, C6H8O6, dissolves in water to form an acidic solution. If a small
amount of magnesium powder is added to the water, the following reaction occurs:
C6H8O6 (aq) + Mg (s)  Mg(C6H6O6)2 (aq) + H2 (g)
(i)
Suggest two observations you would expect to see when the reaction place?
[2]
(ii)
In the above equation, (aq) means in aqueous solution. What do the (s) and (g)
mean?
[1]
(iii)
What is the charge on the asborbate ion, C6H6O6?
(iv)
Describe how would you obtain large crystals of magnesium asborbate from its
aqueous solution.
[2]
b)
Tartaric acid, C4H6O6, is present in wine. What is the empricial formula of tartaric
acid?
[1]
c)
Salts can be produced when the H+ ion of an acid is replaced by a metal ion or an
ammonium, NH4+, ion. These salts usually have high melting and boiling points.
Describe the trend in solubility and electrical conductivity of these salts.
[3]
[1]
8.
This question is about the rates of chemical reactions.
Bisodol is an indigestion relief tablet that it used to relieve heartburn and contains
three active ingredients:
Calcium carbonate (CaCO3)
0.522 g
Magnesium carbonate (MgCO3)
0.068 g
Sodium hydrogen carbonate (NaHCO3)
0.064 g
All these ingredients help to neutralise the excess acidity in the stomach.
a)
Magnesium carbonate, MgCO3 has a structure consisting of two different ions. What
are the formulae of these ions?
[1]
b)
Stomach acid consists mainly of hydrochloric acid. Write a balanced symbol equation
of the reaction between magnesium carbonate and hydrochloric acid.
[2]
c)
The reaction in (b) releases a gas, which is water soluble.
diagram of the apparatus you could you use to collect this gas.
Draw a labelled
[2]
d)
Sometimes it is better to break the tablet into smaller pieces before taking it to
relieve heartburn quicker. Explain why.
[2]
e)
The rate of reaction between magnesium carbonate and hydrochloric acid increases
with temperature. Explain why.
[2]
f)
Increasing concentration of hydrochloric acid can also increase the rate of this
reaction. Explain why.
[1]