ZERAKI ACHIEVERS’ EXAMINATION (2023)
TERM 2 - 2023
CHEMISTRY – (233)
FORM TWO (2)
Time - 2 Hours
Name …………………………………………….……… Admission Number …………….
Candidate’s Signature ………………….…...………... Class ……………………………
INSTRUCTIONS TO THE CANDIDATES:
• Write your name, admission number and date in the spaces provided above
• Answer all the questions in the spaces provided.
• All working must be clearly shown where necessary.
• Mathematical tables and electronic calculators can be used.
For Examiners Use Only
Question Maximum score Candidate’s score
1 13
2 14
3 14
4 09
5 11
6 09
7 10
Total 80
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1. (a) The table below shows some of the properties of period III elements.
Element Q R V X Y Z
Atomic Radii(nm) 0.136 0.099 0.125 0.117 0.110 0.157
Formulae of oxide QO R2O V2O3 XO2 Y2O5 Z2O
Melting point(oC) 650 110 660 119 44.2 97.8
Conductivity Good Poor Good Poor Poor Good
(i) From the table which elements could be:
I. Magnesium………………………………………………………(1mark)
II. Sulphur…………………………………………………………..(1mark)
(ii) Write the formula of the chloride of X. ………………………………...(1mark)
(iii) Arrange the elements as they appear from left to right in the periodic table
(2marks)
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(iv) What type of bonding would you expect the chloride of Y to exhibit? (1mark)
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(v) Write a chemical equation for the reaction of oxide of Y with water. (1mark)
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(b) Use the information in the table below to answer the questions that follow.
Ionization Energy in kJ
Element 1st 2nd 3rd 4th
V 320 580 4900 7200
W 430 4300 6200 8300
X 600 1050 1450 16000
Y 7000 9000 10500 14000
Z 200 420 5200 6600
(i) Name two elements that can be found in the same group? (1mark)
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(ii) To which group does element W belong? Explain. (2marks)
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(iii) Element Y is found to be in Group IV. Write the formula when it reacts with
reacts oxygen gas. (1mark)
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(iv) Which of the elements named in ‘i’ above is more reactive? Explain.(2marks)
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2. (a) Hydrogen can be prepared by reacting zinc with dilute hydrochloric acid.
(i) Write an equation for the reaction (1mark)
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(ii) Name an appropriate drying agent for hydrogen gas. (1mark)
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(iii) Explain why copper metal cannot be used to prepare hydrogen gas. (1mark)
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(iv) Hydrogen burns in oxygen gas to form an oxide. Write an equation for the
reaction. (1mark)
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(v) When zinc is heated to redness in a current of steam, hydrogen gas is
obtained. Write an equation for the reaction. (1mark)
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(b). The set up below is used to investigate the properties of hydrogen.
(i) On the diagram, indicate what should be done for the reaction to occur. (1mark)
(ii) Hydrogen gas is allowed to pass through the tube for some time before it is lit.
Explain. (1mark)
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(iii) Write a chemical equation for the reaction that occurs in the combustion tube.
(1mark)
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(iv) When the reaction is complete, hydrogen gas is passed through the apparatus until
they cool down. Explain. (1mark)
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(v) What property of hydrogen is being investigated? (1mark)
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(vi) Describe how copper could be obtained from the mixture containing copper (II)
oxide. (3marks)
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(vii) Why is zinc oxide not used to investigate this property of hydrogen gas? (1mark)
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3. The table below shows some of the elements of the periodic table and their atomic
numbers, atomic masses and melting point. The letters are not the actual symbols of the
elements
Element B C D E F G H I J K
Atomic 7 8 19 15 2 9 6 16 12 11
Number
Mass 14 16 39 31 4 19 12 32 40 23
number
Melting -209 -218 63 44 -272 223 VARRY 113 669 98
o
point( C)
(a) Select two elements with oxidation state of -3. (2 marks)
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(b) Which elements represent the most powerful reducing agent? (1 mark)
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(c) How does the atomic radii of D compare with that of K. Explain. (2 marks)
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(d) How do you compare the electrical conductivity of element J and K. Give your
reason? (2 marks)
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(e) Select two elements which when reacted with element G forms a compound that
conducts electricity both in molten and aqueous state. (2 marks)
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(f) Select two elements that have a common valency. Name the elements. (2 marks)
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(g) In which group and period does element D belong? (1 mark)
Group ………………………………………………………………………………
Period. ……………………………………………………………………………
(h) Select one element stored in (2 marks)
i) Water……………………………………………………………………
ii) Paraffin………………………………………………………………….
4. Study the reaction scheme below and answer the questions that follow.
(a) Identify substance U and solution V (2marks)
U………………………………………………………………………………………
V………………………………………………………………………………………
(b) Name the reagents necessary for the reactions in the following steps. (2marks)
Step 1
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Step 2
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Step 3
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Step 6
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(c) Give condition necessary for the reaction in step 5 to take place. (1mark)
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(d) Write balanced chemical equations for the reactions in the following steps.
Step 1 (1mark)
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Step 2 (1mark)
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Step 5 (1mark)
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(e) State and explain the observation made in step 5. (1mark)
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5. A form two student was asked to prepare a sample of copper (II) sulphate crystals using
the procedure below.
→ Measure 100cm3 of 2M sulphuric (VI) acid then warm. Add excess copper (II)
oxide powder.
→ Filter the resulting mixture. Heat the filtrate and leave it overnight.
(a) Why was the acid heated before the start of the reaction? (1mark)
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(b) Why was excess copper (II) oxide used? (1mark)
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(c) What was observed when copper (II) oxide was added to the warm acid? (2marks)
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(d) Write an equation for the reaction that took place in (c) above. (1mark)
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(e) Give reasons for carrying out the following processes:
i. Filtration of the mixture. (1mark)
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ii. Heating the filtrate and leaving it overnight (2marks)
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(f) Explain how dry crystals of copper (II) sulphate are finally obtained. (1mark)
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(g) Explain why it would not be possible to prepare copper (II) sulphate salt by
reaction of dilute sulphuric acid with copper metal. (2marks)
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6. The flow diagram below shows the process of obtaining nitrogen from a sample of air.
Use it toanswer the questions that follow
(a) What is the purpose of processes P and Q?
P…………………………………………………………………..………………...(1mark)
Q………………………………………………………………………………...…..(1mark)
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(b) Identify the reagents used in the processes P and Q
P……………………………………………………………………………..……..(1mark)
Q……...………………………………………………………………………...…..(1mark)
(c) Write equations for the reactions taking place during processes P and Q (2marks)
P…………………………………………………………………………………………
Q………………………………………………………………………………...……….
(d) Comment on the purity of the nitrogen gas collected (1mark)
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(e) A student categorized air as a compound and not as a mixture. Give two reasons as to
why the student was wrong (2marks)
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7. Study the information given in the table below and use it to answer the questions that
follow.
Element Description
A An element with 7 protons
B It belongs to period three and has 4 electrons in the outermost energy level
C An element with oxidation number +3 and with 13 protons
D An element that forms its ions by loss of one electron and belongs to period 4
E An element that can be placed in group I or group VII
F An element with the highest number of energy levels and belongs to group II.
G An element with electronic configuration of 2.8.7
H An element with a valiancy of 3. It gains electrons to form ions and belongs to
period 3
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(a) Put the above letters A to H in the correct places in the periodic table below to fit the
descriptions. (4marks)
(b) State the name given to the elements placed in the shaded region. (1mark)
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(c) Draw a dot (.) and cross (x) diagram to show the bonding between the elements F and
G. (1mark)
(d) Compare the atomic radius of elements D and H. Explain. (2marks)
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(e) State two uses of element E (2marks)
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10 | P a g e
