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Centre Number
Candidate
Number
Candidate Name
International General Certificate of Secondary Education
UNIVERSITYOF CAMBRIDGELOCALEXAMINATIONS
SYNDICATE
0620/3
CHEMISTRY
PAPER 3
27 MAY 1999
Thursday
Afternoon
1 hour 15 minutes
Candidates answer on the question paper.
Additional materials:
Mathematical tables.
TIME
1 hour 15 minutes
INSTRUCTIONS TO CANDIDATES
Write your name, Centre number and candidate number in the spaces at the top of this page.
Answer all questions.
Write your answers in the spaces provided on the question paper.
INFORMATION FOR CANDIDATES
The number of marks is given in brackets [ ] at the end of each question or part question.
Mathematical tables are available.
You may use a calculator.
A copy of the Periodic Table is printed on page 12.
FOR EXAMINER'S USE
1
2
3
4
5
TOTAL
This question paper consists of 12 printed pages.
88 (8M) OF91694/3
@ UCLE8 1999
[Turn over
2
1
Lead has been used on roofs since about 5000 BC. It is suited to this use because it is both
malleable and resistant to corrosion. Lead rapidly becomes coated with a layer of basic
lead(II) carbonate that protects it from further corrosion.
(a) (i)
Describe the structure of a typical metal such as lead.
,.............................................................................................
[2]
(ii)
How does the structure of a metal explain why it is malleable?
......
......
,
[2]
(b) Suggest an explanation why exposure to atmospheric pollution changes basic lead(II)
carbonate into lead(II) sulphate.
...
...,
.,
..............
...
.....
"""""""""""""""""""""""""""
[3]
(c) Basic lead(II) carbonate has a formula of the type xPbCO3.yPb(OH)2' where x and y
are whole numbers. Basic lead(II) carbonate was heated in the apparatus shown below.
basic lead
carbonate
t
HEAT
sodium hydroxide,
carbon dioxide
reacts here
ice
(i)
liquid collects
here
How could you show that the liquid collected contained water?
[2]
3
(ii) How could you show that the carbonate gave off carbon dioxide on heating?
[2]
(iii) Explain why sodium hydroxide reacts with the non-metal oxide carbon dioxide.
...................................................................................................................................
[2]
;
(d) Use the following information to calculate x and yand to write the formula for the basic
lead(II) carbonate.
PbCO3
PbO + CO2
Pb(OH)2
PbO + H2O
The basic lead(II) carbonate when heated gave 1.056 g of carbon dioxide and 0.216 g
of water.
The mass of one mole of CO2
=
g
[1]
Number of moles of CO2 formed
-
............
[1]
The mass of one mole of H2O
= 18g
Number of moles of H2O formed
-
Therefore x =
........................
[1]
and y = ............
The formula for the basic carbonate is
.....
........
....
.......
[1]
4
2
In both Europe and the USA, scientists are investigating the use of hydrogen as a fuel for
aeroplanes and cars. It is more efficient and produces less pollution than the existing
petroleum-based fuels.
(a) (i)
Name the fuel obtained from petroleum that is used for jet aircraft.
[1]
(ii)
Name two pollutants formed by the combustion of petroleum fuels and then
explain why the combustion of hydrogen would produce less pollution.
,
.
...................................................................................................................................
,
,
............................................................
[3]
(b) Describe a method of manufacturing hydrogen.
raw material
,........................................
brief description of process.............................................................................................
..........................................................................................................................................
""""""""""""'"
[2]
(c) Hydrogen could be transported in heavy cylinders as a gas under pressure or as a
liquid at low temperatures.
(i)
The pressure exerted by a gas is caused by the molecules of the gas colliding with
the walls of the container. Why would the pressure inside a cylinder increase if the
temperature was increased?
..........
[2]
(ii)
Explain what happens to the molecules in gaseous hydrogen as it changes into a
liquid at -253 aG.
.
......
[3]
5
(d) An alternative method of 'transporting' hydrogen is to change it into methanol. This
liquid is easily transported and can be decomposed to re-form hydrogen. Methanol can
be made by the following reaction.
CO(g) + 2H2(g) ~
CH30H(g)
the forward reaction is
exothermic
The gases are passed over a catalyst at 300 °C.
On cooling, the methanol becomes a liquid.
(i)
The reaction is carried out at high pressure. What effect would this have on the
position of equilibrium?
"
(ii)
.[1 ]
Explain why an increase in pressure would increase the rate of the reaction.
,........................................................
[2]
,
(iii)
What would be the effect of decreasing the temperature on the concentration of
methanol at equilibrium? Give a reasoned explanation for your answer.
,...........................................................................
,.........
.[2]
6
3
(a) The alcohols form a homologous series. Their names, formulae and heats of
combustion are given below. The heat of combustion is the quantity of heat energy
given out when one mole of the alcohol is burned in an excess of oxygen.
name
formula
mass of one mole / g
heat of combustion /
kJ per mole
-720
methanol
CHsOH
32
ethanol
CHsCH20H
46
-1370
propanol
CHsCH2CH20H
60
-2020
butanol
(i)
Complete the last line in the table by writing the formula for butanol, calculating the
mass of one mole and by predicting the heat of combustion.
[3]
(ii)
It is possible to predict physical properties of the members of a homologous series.
Describe two other characteristics of a homologous series.
.......................................................................................
[2]
(iii)
The alcohol CHsCH(OH)CHs is a structural isomer of the propanol in the table.
Explain the term structural isomer.
.
[2]
(b) Give a diagram to show the arrangement of the valency electrons in one molecule of
the covalent compound methanol.
Use x to represent an electron from a carbon atom.
Use 0 to represent an electron from a hydrogen atom.
Use @to represent an electron from an oxygen atom.
[3]
(c) Ethanol can be made from starch. Starch is a complex carbohydrate with a structure of
the type shown.
-0-0-0-0-0-0-
7
This can be broken down by enzymes to simple sugars with formulae of the type shown.
H0
(i)
D-
0H
What other method changes starch into simple sugars?
[2]
(ii)
Give a brief description of how sugars are changed into ethanol.
......
""""""
............
...
...
.[3]
(d) Some alcohols are easily oxidised.
mineral wool
soaked in
propanol
copper(II) oxide
t
HEAT
cold water
chemical formed
by oxidation of
propanol
-------
The chemical formed has a pH of 2. Give the name and structural formula of the chemical
formed.
name
"""""""""
.[1]
structural formula
[1]
8
4
Sulphur production in the USA is about ten million tonnes per year. 90% of this sulphur is
used to make sulphuric acid.
(a) Sulphur dioxide is made by burning sulphur in air. Most of it is used in the Contact
Process. Give one other use of this gas.
[1]
(b) Bacteria can oxidise the sulphur in coal to sulphuric acid. Water draining off coal tips
contains sulphate ions and hydrogen ions.
(i)
Describe how you could show the presence of sulphate ions in the water.
...................................................................................................................................
[2]
(ii)
Without using an indicator, how could you show that the water from the coal tips is
acidic?
"""""""""""""""""""""""""""
,........
[2]
,
(c) In the Contact Process, sulphur dioxide is made by spraying molten sulphur into air.
(i)
Suggest why the molten sulphur is used in the form of a spray.
...
(ii)
,
.[1]
Describe how sulphur dioxide is changed into sulphur trioxide.
......................................................................................................
....................................................................................................
[3]
,
(iii)
Complete the equations for the formation of sulphuric acid from sulphur trioxide.
+
-.
H2S207
+
-.
S03
H2S207
"...H2SO4
[2]
9
(d) Over 50% of the sulphuric acid is used to make fertilisers such as the nitrogen-based
fertiliser ammonium sulphate.
(i)
Give one other use of sulphuric acid.
[1]
""""""""""""""""""""""""""""
(ii)
Nitrogen is one of the three elements essential for plant growth that is added to soil
in fertilisers. Name the other two.
and
(iii)
[2]
The base ammonia is neutralised by sulphuric acid to form ammonium sulphate.
Define the term base.
.....................
.[2]
10
5
You will need to use the Periodic Table of the Elements to answer this question.
(a) A radioactive isotope of the element iodine, 1251, is used to treat cancer. How many
electrons and how many neutrons are there in one atom of this isotope of iodine?
number of electrons
[1]
"
number of neutrons
[1]
(b) Given below are the formulae of the oxides of some of the elements. They are given in
the same order as in the Periodic Table.
MgO
CaO
SiO2
AI203
P203
SrO
(i)
Use the electronic structures of the elements to explain why oxides of elements in
the same group have the same type of formula.
..
.
,...
(ii)
[2]
Use the electronic structures of the elements to explain why oxides of elements in
the same period have different formulae.
.
...
,
,
..,..
,
.............
.......
.[1]
11
(iii)
Complete the table that shows the reaction, if any, of the oxides with acid and
alkali. Indicate a reaction with "R" and no reaction with "NR".
oxide
type of oxide
magnesium oxide
basic
aluminium oxide
amphoteric
silicon(IV) oxide
acidic
reaction with acid
reaction with alkali
[3]
(c)
(i)
Predict the formula for:
the strontium ion,
""""""""""""""""""""""",""""""'"""""""""""""""""""""
the phosphide ion.
(ii)
""""""""""""'[2]
Write the formula for strontium phosphide
[1]
(d) The reactivity of elements in the same group varies in a predictable way.
(i)
Name a metal that reacts more violently with cold water than does potassium.
[1]
(ii)
Complete the word equation.
potassium + water --.
+ ........................................
""""""""""""""""""'"
[2]