THE UNITED REPUBLIC OF TANZANIA .. NATIONAL EXAMlNATIONS COUNCIL CFRTJFICATE OF SECONDARY .EDUCATION EXAMINATION. 032/1 CHEMJS"fRY I (For Both School and Private Candidates) TIME: 3 Hours Tuesday afternoon 09/10/2007 Instructions I. This paper consisis of sections A, B and G. 2. Answer all questions in sections A and B, and two (2) questions from section C. J: All questions carry equal marks. 4. Electronic calculators are not allowed in ihe examination room. 5. Cellular phones arc not allowed in the examination room. 6. Write your Examination Number on every page of your answer booklet(s). 7. The following constants may be used: S4S Atomic masses:H = I; 0 = 16, C = 12, Cu = 63.5, S = 32, Cl = 35.5, Ca = 40, Na 23, N = 14, Fe = 56, Ag, = 108, Au = 197. Atomic numbers: H = I, Cl = 17. Avogadro's constant = 6.02 x J0 23 • GMV at s.t.p. = 22.4 dm 3 . I Faraday = 96500 coulombs. Standard pressure = 760 mm Hg. Standard temperature = 273 K. I litre = I dm 3 = 1000 cm 3 • This paper consists of 8 printed pages. Find more free learning resources at; www.darasaletu.com
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THE UNITED REPUBLIC OF TANZANIA .. NATIONAL EXAMlNA TIONS COUNCIL
CFRTJFICATE OF SECONDARY .EDUCATION EXAMINATION.
032/1 CHEMJS"fRY I (For Both School and Private Candidates)
TIME: 3 Hours Tuesday afternoon 09/10/2007
Instructions
I. This paper consisis of sections A, B and G.
2. Answer all questions in sections A and B, and two (2) questions fromsection C.
J: All questions carry equal marks.
4. Electronic calculators are not allowed in ihe examination room.
5. Cellular phones arc not allowed in the examination room.
6. Write your Examination Number on every page of your answerbooklet(s).
7. The following constants may be used:
S4S
Atomic masses:H = I; 0 = 16, C = 12, Cu = 63.5, S = 32, Cl = 35.5,Ca = 40, Na'= 23, N = 14, Fe = 56, Ag, = 108, Au = 197.
Atomic numbers: H = I, Cl = 17.
Avogadro's constant = 6.02 x J023 •
GMV at s.t.p. = 22.4 dm3.
I Faraday = 96500 coulombs.
Standard pressure = 760 mm Hg.
Standard temperature = 273 K.
I litre = I dm3 = 1000 cm3•
This paper consists of 8 printed pages.
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SECTION A ( 20 marks)
Answer all questions in this section.
I. For each of the items (i) - (x) choose the correcr answer from among the givenultcrnativcs and write its letter beside the item number.
(i)
(ii)
(iii)
(iv)
(v)
A mixture of water and alcohol was carefully distilled. Which property of the first drops of the liquid distillate collected is not correct� The first drops A 8
C D
have the same boiling point as water mix easily with water burn in air are colourless
E will boil at a temperature less than the boiling point of water.
Which oxides are gaseous at room temperature? A Carbondioxide and copper oxide. B Sulphur dioxide and copper oxide. C Carbondioxide and sulphur dioxide. D Copper oxide and iron oxide. E. Iron oxide and carbondioxide.
lf0.5 g·ofhydrogen gas are exploded in air, the. mass of water formed is A 1.8g
.
8 4.5 g C 0.75 g D 4.0 g E 18.g.
A and 8 are--atoms of elements in the same period of the periodic table. A is in group II and B is in group Ill. Which of the following statements is not true? A B has one more proton than A in its nucleus. B The atomic number of B is one unit greater than that of A. C A has cne electron less.than B in its valence shell. D A contains one more electron than B in its valence shell. E A and 8 have the same number of shells.
Which of the following statements is true. The Avogadro's constant is the number of A electrons in one mole of a solid substance B atoms in one mole of any gas at s.l.p C alOms in one mole of a metal D electrons needed to liberate one gram of a univalent metal E electrons released when one mole of any element is discharged at
the anode. .,
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(vi). Which, among the given lisi of metals arranged in order or decreasing _ · ". reactivity with steam from left to right, is correct?
(vii)
(viii)
A Calcium, magnesium. zinc, copper. B Magnesium, calcium, copper, zinc. C C'alr.ii,m, zinc, magnesium, copper. D Zinc, magnesium, copper. calcium. E Calcium, magnesium. copper, zinc.
Scum tend LO ,e formed when washing clothes with hard water due to thereaction between A hard \\ater and soap B calcium ions, magnesium ions and sodium strearate C the dissolved calcium and magnesium salts with detergents D · hydrogen carbonate ions and soapE hydrogen carbonate ions and clothes.
OH belongs to.the homologous series of A alkcnes B. ester�·c alcoho sD alknnesE acids.
(ix) A steady current or 4 amperes was passed through an aqueous solution ofcopper sulphate for 1800 seconds. The mass of copper deposited is
(x)
A 63.5 g B 31.75g C 1.185 g D 2.37 g E 11.85 g.
The particles 1 � M
A isomers B allotropes C molecules D radicals E isotopc-s.
S4S
and liM arc
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2. !\'latch the items in List A with the responses in List B by writing the letter of thecorrect response beside the item number.
' -'.
(i) (ii)
(iii) (iv) (v)
(vi) (vii)
(viii)
(ix) (x)
(a)
List A Double bond functional group ofalkynes Chlorine Empirical formula Pb(N03)2<•q> + Na2COi<:iq>-> PbCOi<sl + 2NaNO,(oql Lead ([I) chloride and silver chloride Elements in the soil needed by plants in large amount
H H
I I 1-1-c-c-:-
�1 I-H..
I
H i'I I I c-y-1-1
I H .C J4H C
I
H H
1 -J
Presence of At3•.and 1 -( ions in the soil Hypothesis
SECTION B (60 marks)
List B
A Soil alkalinity B Double decomposition reaction C Isotope D Isomer of hexane E Bonding in a molecule of
oxygen F Reactiortof conc,entrated HCI
acid on st}Jphur G Soil acidit\,: II Dehydrati6n of s·ugar by
'\ concentrated H2S04 ac)d
J
Simplest formula which expresses the composition of a compound by mass · Common insoluble ·chlorides
K Simplest fonirnla which expresses the actual number of each kind of atoms.p.rcscnt:in-a compound
L Neutralitaiion reaction M A t�ntative statement for the
observed phenonrenon N One of the products of
electrolysis of molten ·sodium Ghloridc
0 Unsaturated hY.drocarbon P Matronu\ricms Q Triple bond R Basic ioris S Theory T Micronulrients
Answer all questions in this section.
(i) What is an ionic bond7(ii) Define a radical.(iii) Draw an electronic diagram to show the covalent bonding between
hydrogen and chlorine in a hydrog,m chloride gas mcilcculc.(iv) Explain why covalent compounds do not conduct c·lcctricity.
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V 4.
(b)
(c)
(a)
(b)
What is the oxidation state of Fe particle.in a FeCh molecule?
Study carefully the electronic co.nfigur'ation of elements Q, Rand S given below then ans,.\er the questions that follow.
Q--2:7R--2:8:1 s--2:6
(i) What type of bond will exist in a compound formed when Qcombines with R?
(ii) In what group and period in the periodic table does element Soccupy? .
(iii) What is the valency of element Q?
(iv) Write a molec.ular formula of a compound formed when element Rcombines\viih S.
Define the term molec·ular formula. An oxide· of iron, 4.5 g by mass, was completely r�duced by heating it in a
certain ·reducing agent and 3.15 g of iron was produced. Calculate the empirical formula of the compound.
(c) When a salt of copper nitrate is heated it undergoes -a chemical change asshown in equation I below.
(i) Balance equation (!).(ii) Wl·,at is the type of chemical reaction represented by equation (I)?
5: The diagrams in figure I below represent common methods of collecting gases in the laboratory.
Method A
S4S
------
- - ----
Method B Fig. I
5
Method C
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6.
7.
(a)
'b) l .
Identify method A, Band C.
Which method is used in ihe laboratory gas preparation of
(i) ammonia'i
(ii) chlorine?
(iii) hydrogen'/
Give reasons for your answers.
(c) What will happen when
(a)
(b)
(C)
(a)
(i) yellow flowers are introduced into a gas jar containing chlorinegas?
(ii) a burning splint is introduced into a gas jar containing hydrogengas?
(iii) a glass rod which was dipped in concentrated hydrochloric acid isintroduced into a gas jar containing ammonia gas?
(iv) sulphur dioxide gas is bubbled through a yellow acidifiedpotassium dichromate solution?
Define the term class B fire.
(i) Mention two (1) combustible materials i_n class B fire.
(ii) Why is water nor used to put off oil fir�s?-
(iii) Your friend's clothes have caught fire. In order to extinguish thefire you have decided to cover her with a damp blanket. What istheJunction of the damp blanket?
(i)
(ii)
(i)
(ii)
Why is air a mixture and not a compound?
Why is rusting of iron a chemical change?.• .
What is a reversible reaction?
List down three (3) factors which affect the position ofequilibriu11 in a reversible chemical reaction.
(b) The industrial preparation of ammonia in the Haber process is representedby the following equation:
Study the equation carefully then answer the questions that follow. Whatwill happen u.'>'the J:>_OSition of equilibrium· if
(i)
(ii)
S4S
the temperature of the equilibrium mixture is increased? . ./
more nitrogen gas is added lO the equilibrium mixtur�?
\
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8.
9.
10.
(c)
(a)
(iii)
(i)
(ii)
the formed ammonia gas is removed from the equilibrium mixture? . Whv are catalysts used in chemical reactions?·· ..
•..
What is the meaning of the negative sign against the value of heat change, -46.2 kJ/mol in the chemical equation given in 7. (b) above?
(iii) Sketch an energy level diagram of energy against reaction path forthe reaction in 7. (b) above.
Classify the following compounds as alkanes, alkenes and alkynes:
C1H12, C.H10, CsH,o. CiH4, C2I-Li and C6H12.
(b) Complete and balance the following chemical equations:
(i) CH esCH+Oi ...:,?
(ii) GH,CH20H + Na ...:,?
(iii) CHiCOOH + KOH ...:,?
(iv) CH2 = CI-h + Cb 4-?
(c) Write down the condensed structural isomers of alcohols of molecularfonnula C4H90H.
(a)
(b)
(a)
(b)
(i)
(ii)
(i)
(ii)
(iii)
SECTION C (20 marks)
Answer two (2) questions from this section.
Define the tenn fertilizer.
What are the three (3) effects of excessive nitrog�n to plants?
State four ( 4) methods o_f application of fertilize.rs.· Wiia.t are the four (4) advantages of using manures in the farms?
Calculate the percentage composition of nitrogen in ammoniumsulphate fertilizer, (NH.)zso •.
Name the ore commonly .. use_d in the extraction of copper metal:
Steps (i) to (iv) below are used during the extraction .of copper metal from. its ore. Write a balanced chemical equation for each step.
(i) Roasting of the concentrated ore (CuFeS2) in air.
(ii) Heating the roasted ore with silica in the absence of air.
(iii) Burning copper sulphide ore (CuS) in regulated supply of air.
(iv) Purification of copper by electrolysis using copper sulphatesolution ele.ctrolyte, pure copper cathode and impure copperobtained from the extraction anode.
S4S
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I I.
12.
..
(c) With the help of chemical equations explain what will happen to
(i) an iron earring dropped into a container of copper sulphatesollltion?
(ii) copper knife dipped into zinc nitrate solution?(iii) copper turnings dropped into a c.ontainer of dilute hydrochloric
acid?
(a) (i) What does the term terrestrial pollution mean?(ii) Mention th rce (3) causes of terrestrial pollution.(iii) Explain four (4) methods of preventing terrestrial pollution.
(b) What is the effect of ultraviolet radiations on living organisms?
(c) (i) Whal is the function of ozone layer in the atmosphere? (ii) What control measures should b� taken to prevent the destruction
of ozone layer?
(a) (i) What are the factors affecting the selective discharge of ions at theelectrodes?
(ii) Define the term electrochemical equivalent.
(b) The apparatus shown in figure 2 below was used in an experiment ofelectroplating an iron knife with silver.��---'G""l'; 11 11 I I :i-::G���
(ii) Write ionic equations to represent the reactions taking place at theelectrodes.
(iii) At which electrode was reduciion taking place?
(c) A sample of impure silver of mass 3.45 g was used as the anode in anelectrolysis purifying process. The cathode was made up of pure gold ofmass 6.45 g. After the electrolysis the cathode was found lO weigh 9.66 g.
(i) Calculate the number of coulombs of electricity passed.(ii) Whal is the percentage purity of the impure silver?
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