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Name _______________________________________________ Index No._______________________
Candidate’s Signature ______________
Date ____________________________
233/1
CHEMISTRY
PAPER 1
THEORY
JULY / AUGUST 2013
2 HOURS
MAKUENI DISTRICT JOINT FORM 4 EXAMINATION 2013
Kenya Certificate of Secondary Education
CHEMISTRY
PAPER 1
THEORY
JULY / AUGUST 2013
2 HOURS
INSTRUCTIONS TO CANDIDATES
1. Write your name and index number in the spaces provided above.
2. Sign and write the date of examination.
3. Answer ALL the questions in the spaces provided in the question paper.
4. Mathematical tables and silent electronic calculators may be used.
5. All working MUST be clearly shown where necessary.
6. This paper consists of 14 printed pages.
7. Candidates should check the question paper to ascertain that all the pages are printed as indicated
and that no questions are missing.
FOR EXAMINER’S USE ONLY
QUESTIONS MAXIMUM SCORE CANDIDATE’S SCORE
1 – 31 80
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This paper consists of 14 printed pages
Turn Over
1. (a) Write the electron configuration of calcium (atomic number 20) and magnesium
(atomic number 12).
Calcium ____________________________ ( ½ mark )
Magnesium _________________________ ( ½ mark)
(b) Explain why calcium is more reactive than magnesium. ( 2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
2. (a) Complete the table below to show the observations made when concentrated
sulphuric (VI) acid is added to the substances shown.
Substance Observation
Crystals of white sugar (i)
Copper (II) sulphate crystals (ii)
(b) Name one fertilizer made from sulphuric (VI) acid. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
3. A solution of chlorine in tetrachloromethane turns colourless when ethene gas is bubbled through it
(a) What type of reaction takes place? (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Write an equation for the above reaction. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
4. The diagram below is a set up of apparatus used to react ammonia gas with iron (II) chloride solution
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Ammonia gas
Funnel
Beaker Iron (II) chloride solution
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 2
(a) State the observation made in the beaker in the first few minutes. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Explain why a funnel is used to deliver the ammonia into the solution. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
5. Study the flow chart below and answer the questions that follow.
Gas Gas
ZnS(s) O2 (g) Zn O (s) Coke Zn (s)
Heat Step 2
Step 1
Step 3 Conc. H2SO4
Zn SO4 (aq) Gas R
(a) What condition is necessary for step 2 to occur? (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Name (i) Gas R ______________________________ (1 mark)
(ii)One use of zinc other than galvanizing iron. (1 mark)
______________________________________________________________________________
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______________________________________________________________________________
______________________________________________________________________________
6. When Xcm3 of 0.5M zinc nitrate solution were reacted with excess ammonium carbonate
solution, the mass of zinc carbonate formed was 12.5g.
(a) Write the ionic equation for the reaction that took place. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 3
(b) Calculate the value of X.
(C = 12.0, Zn = 65.0, O = 16.0 ) (2 marks )
7. Bronze is an alloy of copper and another metal.
(a) Name the other metal __________________________________________________ ( 1 mark)
(b) Give one use of bronze. ( 1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
8. Dilute sulphuric (VI) acid was electrolyzed using the set up represented by the diagram below.
Gas A Bulb Gas B Dilute sulphuric (VI) acid Platinum electrodes
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(a) Write an equation for the reaction that produces gas B. (1 marks )
(b) Describe how gas A can be identified. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 4
(c ) Explain the difference in brightness of the bulb if ethanoic acid is used in place
of sulphuric (VI) acid. ( 1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
9. (a) State Graham’s law of diffusion. ( 1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Gas E takes 110 seconds to diffuses through a porous plug. Gas E has a relative
molecular mass of 34. How long will it take for the same amount of ammonia gas to
diffuse under the same conditions? (N = 14, H = 1 ) ( 2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
10. The scheme below represents the manufacture of a cleansing agent Y.
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Conc. OSO3H
H2SO4
NaOH
Cleansing agent Y
(i) Draw the structure of Y and state the type of cleansing agent to which Y belongs. (2marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(ii) State one advantage of using Y on the environment. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 5
11. The graph below shows volume of hydrogen gas collected against time when a 2cm
magnesium ribbon was reacted with 2M hydrochloric acid.
Volume of H2(g)
produced
Time (sec)
(a) On the same axes sketch the curve Y obtained when a 2cm magnesium ribbon was
reacted with 2M ethanoic acid. (1 mark)
(b) Write an equation for the reaction between ethanoic acid and magnesium. ( 1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
12. The diagram shows an incomplete set-up for the laboratory preparation and collection
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of chlorine gas. Study it and answer the questions that follow.
Conc. HCl Water Black solid Q
(a) Complete the set up to show how dry chlorine gas can be collected. (2 marks )
(b) Name substance Q ______________________________________________ (1 mark )
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 6
13. (a) Write the systematic names of the following compounds.
(i) CH3 CH2 C CCH3 _________________________________ ( 1 mark )
(ii) CH3 CH CH2 OH
CH3 ________________________________ (1 mark )
(b) Draw the structure of 2, 3-dibromobutane. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
14. The diagram below shows how a magnesium is reacted with steam.
Magnesium
Wet cotton Gas C
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(a) Identify the condition required in the set up for gas C to be produced. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Write an equation for the reaction that produces gas C in the set up after the
condition in (a) above is applied. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c ) Why is it not advisable to use sodium in place of magnesium? (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
15 Study the bond energies given below to answer the question that follows.
Bond Bond energy (kJmol-1
)
H – H 432
C = C 610
C – C 346
C – H 413
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 7
Butene can be converted into butane in the equation:
CH3 CH2 CH = CH2 + H2 CH3 CH2 CH2 CH3
Determine the enthalpy change in the reaction. (2 marks )
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16. Water and kerosene are immiscible liquids.
(a) Draw the apparatus that can suitably be used to separate the liquids and label
the layers. (2 marks )
(b) Name the most suitable method used to separate kerosene and petrol. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
17. The diagram below shows some steps used in the manufacture of sodium carbonate by
the solvary process.
Ammonium
Chloride
Ammonium
chloride +
Concentrated sodium CO2 (g) sodium hydrogen Step
chloride Step I carbonate II
Sodium
Substance D Hydrogencarbonate
Step III
Sodium carbonate
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 8
(a) Name substance D ___________________________________________ ( 1 mark )
(b) What process takes place in step II? ( 1 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c ) Write an equation for the reaction taking place in step III. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
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______________________________________________________________________________
______________________________________________________________________________
18. Describe how a solid sample of copper (II) carbonate can be prepared starting with
copper metal. (3 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
19. Sulphur (IV) oxide and nitrogen (IV) oxide gases are released from car exhaust fumes.
Explain two ways these gases affect the environment. ( 2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
20. The table below shows some tests carried out on solid F and the observations made.
Test Observations
I) Heat solid F then cool Solid changed from white to yellow.
II) Add dilute hydrochloric acid to solid F A colourless solution was formed with
effervescence.
III) Add excess sodium hydroxide to the
colourless solution in test III
A white precipitate was formed which dissolved
to form a colourless solution.
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 9
(a) Write the formula of the:
Cation in solid N (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Anion in solid N (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Write the ionic equation for the formation of the colourless solution in step III. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
21. The grid below shows part of the periodic table. The letters used are not the actual
symbols of the elements.
L P
M N
K
(a) Select the:
(i) element with the largest atomic size _________________________________ ( ½ mark )
(ii) most reactive non-metal _________________________________________ ( ½ mark )
(b) On the grid, show the position of element T which forms T3-
ions with electron
configuration 2.8.8 ( 1 mark)
22. (a) A few drops of freshly prepared iron (II) sulphate solution were added to sodium
nitrate solution in a test tube. Concentrated sulphuric acid was added carefully to
the mixture. State the observations that were made. ( 1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) (i) Write an equation for the reaction that occurs when solid sodium nitrate is
strongly heated. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 10
(ii) State the test for the gas produced in b(i) above. (1 mark )
______________________________________________________________________________
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______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
23. When carbon (IV) oxide gas was passed through calcium hydroxide solution, a white
precipitate was formed.
(a) Write an equation for the reaction that took place. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) State and explain the observation made when excess carbon (IV) oxide gas was
bubbled through the white precipitate. ( 2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
24. The table below gives standard electrode potentials for metals represented by the letters
R, S, T and U. Study it and answer the questions that follow.
Metal Standard electrode potential (V)
R -0.13
S -0.76
T + 0.34
U + 0.85
(a) Which metal can be displaced from a solution of its salt by all the other metals in
the table? Give a reason. ( 2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Determine the emf of the cell R / R2+
// U2+
/ U (1 mark )
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 11
25. Study the set-up below and answer the questions that follow.
Gas W
Water
Calcium metal
(a) What physical property of calcium is demonstrated in the set-up? (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Write the equation leading to the formation of gas W. (1 mark )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(c ) State the observation made if the water was replaced with dilute sulphuric (VI) acid. (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
26. (a) The table below shows the pH values of solutions A, B, C, D, E, F, G, and H. Study it and
answer the questions that follow.
Solution A B C D E F G H
pH 1.0 4.0 5.0 6.5 7.0 7.5 8.0 11.0
Select the solution which is likely to be:
(i) Sodium chloride ________________________________________ ( ½ mark )
(ii) Lime water ____________________________________________ ( ½ mark )
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 12
(b) Equal amounts of zinc powder were added to 15cm3 of 1M ethanoic acid and 15cm
3
of 1M hydrochloric acid in separate boiling tubes. The amount of hydrogen gas liberated
after 2 minutes in the boiling tubes was different. Explain this difference. ( 2 marks)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
_______________________________________________________________________________
27. Study the energy level diagram below and answer the questions that follow.
Reactants
Energy
kJmol-1
Products
Reaction path
(a) Identify the kind of reaction represented by the diagram. Explain. (2 marks )
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
(b) Label on the diagram the:
(i) Activation energy, Ea ( ½ mark )
(ii) Enthalpy of reaction, H ( ½ mark )
28. Determine the oxidation number of manganese in:
(i) MnO2 (1 mark )
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(ii) MnO4 - (1 mark )
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 13
29. Copper (II) chloride solution and graphite are both capable of conducting electricity. What is the
major difference between the two substances in their electrical conductivity? ( 1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
30. What is the name given to the smallest repeating unit of a polymer? (1 mark)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
31. The figure below shows a radioactive source. Complete the diagram by showing the
deflection of the different types of emissions. (2 marks )
Radioactive
Source +
Electric field
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.1 14
233/1
CHEMISTRY
PAPER 1
THEORY
JULY / AUGUST 2013
MAKUENI DISTRICT JOINT FORM 4 EXAMINATION 2013
Kenya Certificate of Secondary Education
CHEMISTRY
PAPER 1
THEORY
JULY / AUGUST 2013
MARKING SCHEME
1. (a) C a – 2.8.8.2 1
Mg – 2.8.2 1
(b) The two valence electrons in calcium are further away from the nucleus compared to those
in magnesium and thus they are readily released .
2. (a) (i) The crystals are charred to a black mass // black spongy solid formed.
(ii) Solid changes from blue to white powder .
(b) Ammonium sulphate / (NH4)2SO4
3. (a) Addition reaction
(b) C2H4 + Cl2 C2H4Cl2
Or CH2 = CH2 + Cl2 CH2Cl CH2Cl
4. (a) A green precipitate is formed
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(b) To prevent sucking back / to increase the surface area of absorption since ammonia is
highly soluble.
5. (a) Heat /high temperature
(b) (i) Sulphur (IV) oxide / SO2
(ii) – Batteries / dry cells as the negative terminal
- Electroplating
6. (a) Zn2+
(aq) + CO32-
(aq) ZnCO3 (s)
(b) Moles of ZnCO3 = 12.5
125
= 0.1 moles 1
Mole ratio Zn2+
: ZnCO3 = 1 : 1
Moles of Zn2+
= 0.1 1
0.5M Zn2+
1000cm3
0.1M ?
This paper consists of 5 printed pages
Turn Over
= 0.1 x 1000 1
0.5
= 200cm3
1
7. (a) Tin
(b) Making coins / utensils / statues / belts / jewellery / cabinet handles
8. (a) 4OH- (aq) 2H2O (l) + O2 (g) + 4e
-
(b) Insert a burning splint 1 in a gas jar of gas A. The gas burns with a pop sound 1
to show it is hydrogen gas.
(c ) The bulb is brighter with sulphuric acid 1. Sulphuric acid is a strong acid which is fully
ionized 1 / Ethanoic acid is a weak acid which ionizes partially hence the bulb will dim.
9. (a) Under the same condition of temperature and pressure, the rate of diffusion of a gas is
inversely proportional to the square root of its density.
(b) TE = ME NH3 = 14 + 3 = 17 1
TNH3 MNH3
110 = 34
TNH3 17 1
TNH3 = 110
2 1
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= 77.78 sec
10. (i)
OSO3Na
Soapless detergent 1
(ii) Pollutes the environment since it is non-biodegradable
11. (a)
Volume of H2(g)
produced 1
Curved Y 1
Time (sec)
(b) Mg(s) + 2CH3 COOH (aq) (CH3COO)2Mg (s) + H2 (g)
2
12 (a) Concentrated sulphuric acid Dry chlorine
- Workability of set-up
- Suitable drying agent 1
- Collection method 1
(b) Manganese (IV) oxide / Mn O2 (s) / Lead (IV) oxide / PbO2 (s)
13. (a) (i) Pent-2-yne
(ii) 2-methylpropan-1-ol
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(b) H Br H H
H C C C C H
H H Br H
14. (a) Heat
(b) Mg (s) + H2O (g) MgO (s) + H2 (g)
(c ) Sodium reacts explosively with steam
15. H – E bonds broken + E bonds formed
= 3 (C –H ) + C = C + H – H + 5 (C – H) + C – C
= 3(413) + 610 + 432 + - (5(413) + 346)
= 2281 – 2411
= -130kJmol-1
16. (a) Kerosene Water
- Diagram
- Labelling – Kerosene floating 1
- Water bottom 1
(b) Fractional distillation
3
17. (a) Ammonia
(b) Filtration / crystallization
(c ) 2Na HCO3 (s) Na2 CO3 (s) + CO2 (g) + H2O (l)
18. Add excess copper metal to concentrated nitric acid 1 in a beaker / Add excess copper metal
to concentrated sulphuric (VI) acid.
- Filter out the excess / unreacted copper 1
- Add aqueous sodium carbonate or potassium carbonate to the filtrate 1
- Filter the resulting mixture 1 and wash the residue 1
- Dry the residue 1 between filter papers.
NB: Reject dilute HNO3 / H2SO4 / HCl
19. - The two gases dissolve in rain water in the atmosphere causing acid rain which is harmful to
plants and corrodes concrete and iron structures.
- The two gases are poisonous so inhalation can cause respiratory disorders
20. (a) (i) Zn2+
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(ii) CO32-
(b) Zn(OH)2 (s) + 2OH- (aq) [ Zn (OH)4]
2- (aq)
21 (a) (i) K
(ii) P
(b) Group 5, period 3 on the grid
22. (a) A brown ring was seen at the junction between the two layers of liquids.
(b) (i) 2NaNO3 (s) Heat 2NaNO2 (s) + O2 (g)
(ii) Relights a glowing splint
23. (a) Ca(OH)2 (aq) + CO2 (g) CaCO3 (s) + H2O (l)
(b) The white precipitate dissolves forming a colourless solution . The white calcium carbonate
and water reacts with carbon (IV) oxide producing soluble calcium hydrogen carbonate 1
24. (a) U. It is the weakest reducing agent / has weakest reducing power / most easily
reduced / has highest +ve potential / is the strongest oxidizing agent.
(b) Emfcell = E reduced – Eoxidized
= 0.85 – (-0.13(1
= + 0.98V 1
25. (a) It sinks in water /denser than water
(b) Ca(s) + 2H2O (l) Ca(OH)2 (aq) + H2(g)
(c ) The reaction proceeds for a short time then stops
26. (a) (i) E 1
(ii) H 1
4
(b) More hydrogen gas was produced in the reaction involving hydrochloric acid .
Hydrochloric acid is a strong acid which produces more hydrogen ions in the reaction
hence more hydrogen gas.
27. (a) Exothermic reaction . The products have lower energy than the reactants
(b)
Reactants Ea
Energy
kJmol-1
H
Products
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Reaction path
28. (i) + 4
(ii) + 7
29. Copper (II) chloride solution conducts by mobile ions while graphite conducts by delocalized
electrons
30. Monomer
31.
NB: has more deflection than
Radioactive
Source
+
Electric field
5
Name _______________________________________________ Index No._______________________
Candidate’s Signature ______________
Date ____________________________
233/2
CHEMISTRY
PAPER 2
THEORY
JULY / AUGUST 2013
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2 HOURS
MAKUENI DISTRICT JOINT FORM 4 EXAMINATION 2013
Kenya Certificate of Secondary Education
CHEMISTRY
PAPER 2
THEORY
JULY / AUGUST 2013
2 HOURS
INSTRUCTIONS TO CANDIDATES
1. Write your name and index number in the spaces provided above.
2. Answer ALL the questions in the spaces provided.
3. Mathematical tables and silent electronic calculators may be used.
4. All working MUST be clearly shown where necessary.
FOR EXAMINER’S USE ONLY
QUESTIONS MAXIMUM SCORE CANDIDATE’S SCORE
1 13
2 12
3 10
4 11
5 9
6 11
7 14
TOTAL 80
This paper consists of 15 printed pages
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1. The table below contains some information of elements belonging to the same group on the periodic
table. (The letters are not actual symbols of the elements). Use it to answer the questions that
follow.
Element Ionisation energy Standard electrode
potential ‘E’
Atomic radius
(nm)
Ionic radius
(nm) First Second
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W 549 1064 -2.89 1.91 1.13
X 738 1451 -2.37 1.36 0.65
Y 502 965 -2.90 1.98 1.35
Z 589 1145 -2.87 1.74 0.97
(a) (i) What is ionization energy? (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) Explain why the second ionization energy is higher than the first ionization energy. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(b) Which of the elements is the most reactive? (1 mark)
___________________________________________________________________
Give a reason for your answer. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(c ) Arrange the elements according to the way they appear in the periodic table down the group. ( 1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(d) A cell was made by connecting two half-cells of elements X and Y. Work out the e.m.f
of the cell. ( 1 mark )
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 2
(e) Element W was to be extracted from its ore. What would be the most suitable method to use?
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____________________________________________________________________
Give a reason for your answer. (2 marks )
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(f) Limestone is a common compound in many areas and it affects the quality of water originating
from such areas.
(i) What is the chemical name for limestone? (1 mark )
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) What type of water hardness is caused by the presence of limestone? (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(iii) The set up below was used to remove hardness of water. Identify this method. (1 mark)
Na+ Na
+
Na+ Na
+
Na+ Na
+
Na+ Na
+
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(iv) The above system eventually lacks the ability to soften hard water. Explain how it can be
reactivated. ( 1 mark)
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 3
(v) State one advantage of hard water. (1 mark)
_____________________________________________________________________________
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2. (A) The table below gives some information about some oxides. Study the information and answer the
questions that follow.
Formulae
of oxide
Melting
point
Effect of adding
water to oxide
Effect of electric current on
molten oxide
Effect of adding
aqueous sodium
hydroxide to oxide
Na2O 920 Dissolves readily Conducts electricity Na(s)
and O2 are produced
(a)
P2O5 563 Dissolves readily (b) (c )
SO3 17 Dissolves readily Does not conduct Reacts readily
Al2O3 2045 Does not dissolve
readily
(d) Reacts readily
(a) Complete the table by filling the blank spaces a to d . (2 marks )
(b) Write equations for the reactions that take place between.
(i) SO3 (g) and water. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) SO3 (g) and sodium hydroxide. (1 mark)
_____________________________________________________________________________
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(c ) Why is it not advisable to carry out reaction b(i) above in the laboratory? (1 mark)
_____________________________________________________________________________
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(d) Explain the difference between the melting point of P2O5 and SO3. (1 mark)
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 4
(e) Phosphorus (V) oxide dissolves in water to form phosphoric acid. Explain how the ability
of concentrated phosphoric acid to conduct an electric current compare to that of dilute
phosphoric acid. (2 marks )
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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2. (B) The reaction scheme below is for the industrial manufacture of hydrochloric acid.
Hydrogen gas
Water
Chlorine gas Burning Gaseous
Chamber substance
Glass beads
Tap
Tap
Hydrochloric acid
(i) Write an equation for the reaction that occurs in the burning chamber. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) What is the purpose of the glass beads in the absorption chamber. (1 mark)
_____________________________________________________________________________
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_____________________________________________________________________________
_____________________________________________________________________________
(iii) Given the percentage purity of the hydrochloric acid manufactured is 35% and its
density is 1.18g/cm3. Determine the concentration of the acid ( H = 1, Cl = 35.5 ) ( 2 marks )
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 5
3. The apparatus shown below were used to determine the molar heat of displacement of copper.
Thermometer Polystyrene cup Copper (II) sulphate + zinc metal solution Plastic beaker
1.0g of zinc powder was added to 50cm3 of 0.2M copper (II) sulphate solution and the mixture stirred
gently. The temperature rose from 210C to 28
0C.
(a) Explain the reason why?
(i) A glass rod was used to stir the mixture instead of iron. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) Polystyrene cup was used instead of a glass beaker. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(b) Write a chemical equation for the above reaction. (1 mark)
_____________________________________________________________________________
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_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(c ) Calculate:-
(i) The number of moles of copper (II) sulphate solution. (1 mark)
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 6
(ii) The molar heat of displacement of copper (specific heat capacity of
solution = 4.2 J/g/k, density of solution = 1g/cm3 (2 marks )
(d) Why is the molar heat of displacement obtained in c(ii) above lower than the actual value? (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(e) Draw an energy level diagram for the reaction above. (2 marks )
(f) If magnesium ribbon was used in place of zinc, compare the H value with that of zinc.
Give a reason. ( 1 mark )
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4.(a) The flow chart below shows a series of reactions starting with propanol. Study it and
answer the questions that follow.
Polymer F Process 3 A Hydrogen chloride E
Gas
Process 1
Conc. H2SO4 1700C
B KMnO4 / H+ Propanol Propanoic acid C
H2SO4 (l) Process 2
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 7
(i)Name products: (1½marks)
A _____________________________________
B _____________________________________
C _____________________________________
(ii) Name processes (1½marks)
Process 1 ______________________________________
Process 2 ______________________________________
Process 3 ______________________________________
(iii) Draw the structural formulae of the products E and B
E (1 mark) B ( 1 mark )
(iv) In what class of compounds does product C belong? ( 1 mark)
_____________________________________________________________________________
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_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(v) Draw the structural formulae of polymer F with two repeating units. (1 mark)
(vi) State two advantages of using synthetic polymers. ( 1 mark)
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 8
(b) Study the diagram below and answer the questions that follow.
Flame Gas R to sunction pump Ice salt mixture Substance P Butane
(i) Write an equation for the combustion reaction. (1 mark)
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_____________________________________________________________________________
_____________________________________________________________________________
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(ii) The pH value of a solution of substance R is found to be less than 7. Explain this
observation. ( 1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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(iii) Explain why butanol is soluble in water unlike butane gas. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 9
5. The flow diagram below shows some reactions of dry air. Study it and answer the
questions that follow.
Solid F
Dry air Copper
Heat
Magnesium + Mixture of NaOH (aq) Gas Y
Heat gases Step I
350 atm Step II
4500C and
finely Gas D
Solid A Solid B divided iron
Water Gas Z
Substance C Gas X
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(a) Identify the following (2 marks )
(i) Solid A _____________________________________
(ii) Solid B _____________________________________
(iii) Gas D _____________________________________
(iv) Gas Z ______________________________________
(b) Why is the amount of solid B obtained much less than solid A? (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(c ) Write a balanced chemical equation for the reaction between solid B and water. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(d) How can gas Y be obtained from gas X in the laboratory? Explain using a chemical equation. (2 marks)
_____________________________________________________________________________
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 10
(e) Which gas is absorbed by sodium hydroxide in step I. ( ½ mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(f) Gas Y obtained in step I is impure, name one impurity it contains. ( ½ mark )
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(g) (i) What is the name given to the process that occur in step II. ( 1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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(ii) Explain the effect of using much lower temperature than that in step II. (1 mark )
_____________________________________________________________________________
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6. The flow chart below outlines some processes involved in the extraction of copper from copper
pyrites. Study it and answer the questions that follow.
Ore P Powdered Concentrate
Ore
Air Hot air
Gas L
2nd
roasting Cu2S Smelting 1st roasting
furnace furnace furnace
Cu2S Slag M
Cu2O Compound
G
Gas L
Impure copper J Pure copper
(a) Name the following: (2 marks )
(i) Ore P ______________________________________
(ii) Gas L ______________________________________
(iii) Slag M ____________________________________
(iv) The impure copper J __________________________
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 11
(b) (i) Explain how the ore is concentrated. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(ii) Why is it necessary to grind the ore into powder. ( ½ mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
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(c ) Give the purpose of adding silicon (IV) oxide compound G into the smelting furnace. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(d) Pure copper is obtained from impure copper by electrolysis. Name the material used as anode,
cathode and electrolyte. (1½ marks)
Anode __________________________________________
Cathode _________________________________________
Electrolyte _______________________________________
(e) What effects does this process of copper extraction have to the environment. (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(f) State two uses of copper metal. (2 marks )
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(g) A current of 100 Amperes was passed for 20 days. Hat mass of copper in kg was
deposited at the cathode. (Cu = 64, If = 96500 C ) (2 marks )
MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 12.
7. (i) The table below shows the results obtained when sodium carbonate was reacted with excess 0.5m
sulphuric (VI) acid at room temperature.
Time sec 0 10 20 30 40 50 60 70 80
Volume of CO2 (cm3 ) 0 35 61 82 95 100 103 105 105
(a) On the grid provided, plot a graph of the volume of CO2 against time. (3 marks )
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 13
(b) Use the graph to determine volume of CO2 evolved at 25th
second. (1 mark)
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(c ) At what time did the reaction stop? (1 mark)
(d) Write a balanced chemical equation to show the reaction that took place between sodium
carbonate and sulphuric (VI) acid. ( 1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(e) Calculate the mass of sodium carbonate used in this reaction. (Na = 23, C = 12, O = 16,
volume of gas at r.t.p = 24dm3 ) ( 2 marks )
(f) If the same experiment was repeated using excess 1.0M sulphuric acid instead of 0.5M
sulphuric acid. What would be the effect on the time taken. ( 1 mark)
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_____________________________________________________________________________
_____________________________________________________________________________
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 14
7. (ii) 12g of a mixture of sodium carbonate and sodium sulphate were mixed with distilled water in
a flask and topped up to 1,000cm3. 25cm
3 of this solution required 12.5cm
3 of 0.2M
sulphuric (VI) acid for complete reaction.
(a) Which substance in the mixture reacted with dilute sulphuric (VI) acid solution? (1 mark)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
(b) Calculate the number of moles of the sulphuric (VI) acid which recated with the substance. (1 mark)
(c ) Determine the number of moles of the substance in (a) above which took part in the reaction. (1 mark)
(d) Determine the molarity of the substance which reacted with sulphuric (VI) acid. (1 mark)
(e) What is the mass of the substance which reacted in the mixture?
Na = 23, C = 12, O = 16, S = 32 ) (1 mark )
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MAKUENI DISTRICT JOINT FORM IV EXAM 2013 CHEMISTRY P.2 15
233/2
CHEMISTRY
PAPER 2
THEORY
JULY / AUGUST 2013
MAKUENI DISTRICT JOINT FORM 4 EXAMINATION 2013
Kenya Certificate of Secondary Education
CHEMISTRY
PAPER 2
THEORY
JULY / AUGUST 2013
MARKING SCHEME
1. (a) (i) The amount of energy required to remove an electron from an atom in gaseous state.
(ii) The second ionization electron is removed from an already positive or charged ion.
(b) Y
Reason: Y has the largest atomic radius which means electrons are loosely attracted to the
nucleus hence easily removed.
(c ) X, Z, W, Y
(d) Ered – Eoxd
= -2.37 – (-2.90)
= -2.37 + 2.90 = 0.53V
(e) Electrolysis
Reason: It is a very reactive element and the common reducing agents would not reduce
its ore.
(f) (i) Calcium carbonate
(ii) Temporary hardness
(iii) Ion exchange method or permutit or zeolite process.
(iv) Wash with brine / concentrated / saturated sodium chloride.
(v) - Formation of strong teeth or bones
- Formation of animal shells Any correct one
- Lead pipes do not dissolve NB: One must be one, if more are given
They must be correct if not
correct, no score
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2. (A) (a) a – No reaction
b – Does not conduct
c – Readily reacts
d – Conducts electricity AL(s) and O2 are produced.
This paper consists of 6 printed pages
Turn Over
(b) SO3 (g) + H2 O (l) H2 SO4 (aq) NB; If letters are joined, No score
- If state symbols are missing even if it is
one or it is wrong penalize ½ mk
(ii) S O3 (g) + 2 Na OH (aq) Na2 SO4 (aq) + H2 O (l)
(c ) Recation is highly exothermic producing mist of acid droplets in air.
(d) Both P2 O5 and SO3 molecules are linked up by van der waals forces, they are stronger
in P2 O5 which is a larger molecule compared to SO3.
(e) Concentrated phosphoric acid is a poor conductor because it is only partially dissociated and
has few ions, where as dilute phosphoric acid is a better conductor because it is fully
dissociated with many or more ions.
2. (B) (i) Cl2 (g) + H2 (g) 2HCl (g) ( 1 mark)
(ii) To increase the surface area of absorption. (1 mark)
(iii) Mass of HCl in 1cm3 = 1.18g
= 1.18 x 35
/100 = 0.413g ½
Mass of HCl in 1,000cm3 0.413 x 1000 = 413g ½
Molarity = mass / litre
RMM
= 413 ½
36.5 = 11.32M ½
3. (a) (i) Iron being higher than copper in the reactivity series will go in solution displacing Cu2+
ions. Glass has no effect (1mk) / Iron will absorb some of the heat produced.
(ii) Polystyrene is a poor conductor of heat than glass therefore no heat loss. 1mk
(b) CuSO4 (aq) + Zn (s) Zn SO4 (aq) + Cu (s)
NB: Penalise
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- Missing state symbols ½ mk or incorrect
- Joined letters fully penalize
(c ) Calculate:
(i) No.of moles = molarity x volume
1000
= 0.2 x 50
1000
= 0.01 moles
(ii) Heat = mass x specific heat capacity x temperature change
MCT
= 50 x 4.2 x ( 28 – 21 )
= 1470J NB: Penalise for small letter J i.e j
2
0.01 moles give 1470J
1 mole ?
1 x 1470 = 147,000J
0.01
= 147KJ / Mole
(d) - Assumption that solution has some density and specific capacity as water.
- Neglecting mass of zinc used.
- Neglecting heat capacities of beaker, metal and thermometer.
(e)
NB; Labelling Axis – ½ mk
Showing reactants above products – 1mk
Zn (s) + Cu SO4 (aq) Enthalpy change – ½ mk
-147KJ
ZnSO4 (aq) + Cu (s)
Reaction path / process ½
(f) H value with magnesium will be higher than with zinc. Magnesium is higher in the
reactivity series. Mg is more reactive than zinc.
4. (a) (i) A – Propene
B – Propanoic acid
C – Propylpropanoate
(ii) Processes 1 – Dehydration
Processes 2 – Esterification
Processes 3 – Polymerisation
Ener
gy K
JMol-1
½
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(iii) A) H H H B) H H
O
H C C C Cl H C C C
OH
H H H H H
(iv) Esters
(v) H CH3 H CH3
C C C C
H H H H n
(v) - Are cheap.
- Can be mould into many complex shapes.
- Resistant to corrosion by acids, alkalis, air and water.
- Colourful and attractive. (Any 2 each ½ )
3
(b) (i) 2C4 H10 (g) + 13O2 (g) 8CO2 (g) + 10H2 O (g)
(ii) Carbon (IV) oxide is acidic gas, it dissolves in water to form a weak carbonic acid
hence the Ph is below 7.
(iii) Butanol has a polar end ( O – H) which establishes hydrogen bonds with the water
molecules unlike butene which is molecular.
5. (a) (i) Solid A – Magnesium oxide
(ii) Solid B – Magnesium nitride
(iii) Gas D – Hydrogen gas
(iv) Gas Z – Ammonia gas
(b) Oxygen is more reactive than nitrogen, hence reacts faster and completely with magnesium,
nitrogen is less reactive and a little of it (N2) reacts with magnesium.
(c ) Mg3 N2 + 6H2 O (l) 3Mg(OH) 2 (s) + 2NH3 (g)
(d) Pass gas X, NH3 through heated copper (II) oxide. The ammonia will be oxidized to
nitrogen gas.
2NH3 (g) + 3Cu O(s) N2 (g) + 3Cu (s) + 3H2O (l)
(e) Carbon (IV) oxide
(f) Helium, Neon, Argon or any other Noble gas
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(g) (i) Haber process
(ii) More ammonia gas will be produced
Low temperature favours forward reaction since it is exothermic
6. (a) (i) Copper pyrites or (Cu FeS2)
Gas l – Sulphur (IV) oxide
Slag M- Iron (II) silicate / Fe SiO3
J – Blister copper
(b) (i) Through froth floatation, it is mixed with water, oil and air and then stirred.
(ii) To increase surface area.
(c ) To facilitate removal of iron (II) oxide impurity
FeO (s) + Si O2 (s) FeSiO3 (s)
(d) Anode – Impure copper
Cathode – Strips of pure copper
Electrolyte – Copper (II) sulphate
(e) Pollutes the environment as the sulphur (IV) oxide produced is an air pollutant.
(f) Making electrical wires.
Making soldering instruments.
Making alloys e.g brass (Cu, Zn) brinze (Cu + Tin)
4
(g) Q = 1t
= 100 x 20 x 24 x 60 x 60
= 172, 800, 00oC ½
2 x 96500C deposit = 64g of Cu
172,800,000C ?
172,800,000 x 64 ½ = 57301.5544g ½
193,000
Mass in kg = 57301.5544 = 57.3kg of copper ½
1,000
7. (i) (a) Scale = 1
Plotting = 1
Smooth curve = 1
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5
7. (ii) (a) Sodium carbonate (Na2 CO3 )
(b) Molarity of H2 SO4 = 0.2M
0.2 moles = 1,000cm3
? 12.5cm3
0.2 x 12.5
1,000 = 0.0025 moles
(c ) Na2 CO3 (aq) + H2 SO4 (aq) Na2 SO4 (aq) + CO2 (g) + H2 O (l)
From the mole ratio moles of Na2 CO3 = moles of H2 SO4
= 0.0025 moles
(d) 25cm3 of Na2 CO3 contains 0.0025 moles
1000cm3 ?
1,000 x 0.0025
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25
= 0.1 moles in 1000cm3
Molarity of Na2 CO3 = 0.1M
(e) R.M.M of Na2 CO3 = 46 + 12 + 48 = 106
1 mole = 106g
0.1 mole ?
0.1 x 106 = 10.6g
1
7. (b) 71cm3 1cm
3
(c ) 70th
second
(d) Na2 CO3 (s) + H2 SO4 (aq) Na2 SO4 (aq) + H2 O (l) + CO2 (g)
(e) Mole ratio Na2 CO3 : CO2
1 : 1
1 mole 24,000cm3
? 105cm3
105 x 1 = 0.004375 moles
24,000
Mole ratio = 1 : 1
Moles of Na2 CO3 = moles of CO2 = 0.004375
Moles = mass
RMM
0.004375 = x
106
X = 106 x 0.004375
= 0.46375g
(f) Time will shorten or will be less.
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