International General Certificate of Secondary Education ... · PDF fileCHEMISTRY 0620/3 PAPER 3 Thursday 27 MAY 1999 Afternoon 1 hour 15 minutes Candidates answer on the question

Centre NumberCandidateNumber

Candidate Name

International General Certificate of Secondary EducationUNIVERSITYOF CAMBRIDGELOCALEXAMINATIONSSYNDICATE

CHEMISTRY 0620/3PAPER 3

Thursday 27 MAY 1999 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.

This question paper consists of 12 printed pages.88 (8M)OF91694/3@ UCLE8 1999 [Turn over

FOR EXAMINER'S USE

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1 Lead has been used on roofs since about 5000 BC. It is suited to this use because it is bothmalleable and resistant to corrosion. Lead rapidly becomes coated with a layer of basiclead(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 yare whole numbers. Basic lead(II) carbonate was heated in the apparatus shown below.

basic leadcarbonate

t

sodium hydroxide,carbon dioxide

reacts here

HEAT

ice liquid collectshere

(i) 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 basiclead(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 gof water.

The mass of one mole of CO2 = g [1]

[1]Number of moles of CO2 formed - ............

The mass of one mole of H2O = 18g

Number of moles of H2O formed - ........................ [1]

Therefore x = 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 foraeroplanes and cars. It is more efficient and produces less pollution than the existingpetroleum-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 thenexplain 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 aliquid at low temperatures.

(i) The pressure exerted by a gas is caused by the molecules of the gas colliding withthe walls of the container. Why would the pressure inside a cylinder increase if thetemperature was increased?

..........

[2]

(ii) Explain what happens to the molecules in gaseous hydrogen as it changes into aliquid at -253 aG.

. ......

[3]

5

(d) An alternative method of 'transporting' hydrogen is to change it into methanol. Thisliquid is easily transported and can be decomposed to re-form hydrogen. Methanol canbe made by the following reaction.

CO(g) + 2H2(g) ~ CH30H(g) the forward reaction isexothermic

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 theposition of equilibrium?

" .[1 ]

(ii) 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 ofmethanol at equilibrium? Give a reasoned explanation for your answer.

,...........................................................................

,.........

.[2]

6

3 (a) The alcohols form a homologous series. Their names, formulae and heats ofcombustion are given below. The heat of combustion is the quantity of heat energygiven out when one mole of the alcohol is burned in an excess of oxygen.

(i) Complete the last line in the table by writing the formula for butanol, calculating themass 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 ofthe 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 ofthe type shown.

-0-0-0-0-0-0-

name formula mass of one mole/ gheat of combustion /

kJ per mole

methanol CHsOH 32 -720

ethanol CHsCH20H 46 -1370

propanol CHsCH2CH20H 60 -2020

butanol

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This can be broken down by enzymes to simple sugars with formulae of the type shown.

H0 D- 0 H

(i) 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 woolsoaked inpropanol

copper(II) oxide

tHEAT cold water

chemical formedby oxidation ofpropanol

-------

The chemical formed has a pH of 2. Give the name and structural formula of the chemicalformed.

name """"""""" .[1]

structural formula

[1]

8

4 Sulphur production in the USA is about ten million tonnes per year. 90% of this sulphur isused to make sulphuric acid.

(a) Sulphur dioxide is made by burning sulphur in air. Most of it is used in the ContactProcess. Give one other use of this gas.

[1]

(b) Bacteria can oxidise the sulphur in coal to sulphuric acid. Water draining off coal tipscontains 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 isacidic?

""""""""""""""""""""""""""" ,........

, [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.

... , .[1]

(ii) Describe how sulphur dioxide is changed into sulphur trioxide.

......................................................................................................

....................................................................................................

, [3]

(iii) Complete the equations for the formation of sulphuric acid from sulphur trioxide.

S03 + -. H2S207

H2S207+ -. "...H2SO4[2]

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(d) Over 50% of the sulphuric acid is used to make fertilisers such as the nitrogen-basedfertiliser 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 soilin fertilisers. Name the other two.

and [2]

(iii) 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 manyelectrons 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 inthe same order as in the Periodic Table.

MgOCaO

SrO

AI203 SiO2 P203

(i) Use the electronic structures of the elements to explain why oxides of elements inthe same group have the same type of formula.

..

.

,... [2]

(ii) Use the electronic structures of the elements to explain why oxides of elements inthe same period have different formulae.

. , ..,.. .............

... , , .......

.[1]

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(iii) Complete the table that shows the reaction, if any, of the oxides with acid andalkali. Indicate a reaction with "R" and no reaction with "NR".

[3]

(c) (i) Predict the formula for:

the strontium ion, """"""""""""""""""""""",""""""'"""""""""""""""""""""

the phosphide ion. """"""""""""'[2]

(ii) 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]

oxide type of oxide reaction with acid reaction with alkali

magnesium oxide basic

aluminium oxide amphoteric

silicon(IV) oxide acidic