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Chemistry Paper One Question Paper
Chemistry Paper One
Course:Secondary Level
Institution: Kcse question papers
Exam Year:2011
NAME……………………………………………………………INDEX NO…………..
233/1 CANDIDATES SIGN………..
CHEMISTRY DATE…………………
PAPER I
(THEORY)
TIME: 2 HOURS
JULY/AUGUST 2011
FORM FOUR CLUSTER EXAMINATION 2011
Kenya Certificate of Secondary Education (K.C.S.E)
INSTRUCTIONS TO CANDIDATES
a) Write your name and index number in the spaces provided above.
b) Sign and write the date of examination in the spaces provided above
c) Answer all the questions in the spaces provided
d) Mathematical tables and electronic calculators may be used
e) All working must be clearly shown where necessary.
FOR EXAMINERS USE ONLY
QUESTION MAXIMUM SCORE CANDIDATES SCORE
1 - 30 80
This paper consists 11 Printed pages
Turn over
1. a) What is meant by allotropy? (1 mark)
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b) The diagram below shows the structure of one of the allotropes of carbon
i) Identify the allotrope (1/2 mark)
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ii) State one property of the above allotrope and explain how it is related to its structure. (1 ½ marks)
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2. Pentane and ethanol are miscible. Describe how water can be used to separate a mixture of pentane and ethanol. (3 marks)
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3. a) Using dots and cross diagram, show how a hydro-axonium ion, H3O+ if formed
Hint: H20 +H+ H3O+ Atomic numbers (H= 1, O = 8) (2 marks)
b) What name is given to the bonding in (a) above. (1 mark)
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4. In the redox reaction below:
2H+(aq) + Cr2072-(aq) + 3SO2 (aq) Cr3+(aq) + 3SO2-4 +H20(l)
Identify the reducing agent, explain your answer. (2 marks)
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5. 60cm3 of oxygen gas diffused through a porous hole in 50 seconds. How long will it take 80cm3 of sulphur(iv) oxide to diffuse through the same hole under the same conditions. (3 marks)
(S= 32.0. O=16.0)
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6. Calculate the heat of formation of carbon (II) oxide from the following data. (2 marks)
C(s) + 02(g) CO(g) ?H = -394.8kj/mol
CO(g) + 1/2O2(g) CO2 ?H = -285.6kj/mol
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7. a) Draw and name the structure of the compound formed when one mole of ethyne reacts with one mole of hydrogen bromide. (1 mark)
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b) Draw and name the structural isomers of C4H8 (2 marks)
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8. The table below gives the atomic numbers of element w, x, y and z. The letters do not represent the actual symbols of the elements.
Element w x y Z
Atomic number 9 10 11 12
a) Which one of the elements is least reactive? Explain (1 mark)
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b) (i) Which two elements would react most vigorously with each other? (1 mark)
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(ii) Give the formula of the compound formed when elements in (i) above react. (1 mark)
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9. Dry ammonia gas was made to dissolve in water using the set of apparatus shown below
Dry ammonia gas
Funnel
Red litmus paper
Water
a) What is the use of the inverted funnel (1 mark)
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b) Give and explain the observation made on the litmus paper. (1 mark)
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10.The solubility of potassium nitrate is 85g/100g of water at 50oc and 32g/100g of
water at 25oc.
a) Define the term solubility. (1 mark)
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b) Calculate the mass of the crystals formed if a saturated solution of potassium
nitrate in 50g of water at 50oc is cooled to 25oc. (2 marks)
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11. The following are observations made from two solid substances x and y.
Solid Electrical conductivity in solid state Solubility in water Boiling point
X Poor Insoluble Sublimes
y poor soluble high
a) State the most likely type of bonding in
(i)Solid x ……………………………………………………. (1 mark)
(ii) Solid y……………………………………………………. (1 mark)
12. What is the oxidation number of Nitrogen in
a) HNO2 ……………………………………………………………………… (1 mark)
b) NH4+ …………………………………………………………………… (1 mark)
13. Study the scheme below and answer the questions that follow.
Step I Cl2(g)
Step II Step III
Addition Heat
Of NaOH and Filtration
i) Write down the formula of the yellow solid F. (1 mark)
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ii) What property of chloride is shown in step I (1 mark)
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iii) Write an equation for the reaction which occurs in step III (1 mark)
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14. When air is bubbled through pure water (PH=7) the PH drops to 6.0. Explain. (2 marks)
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15. Temporary water hardness can be removed by boiling
a) What is hard water. (1 mark)
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b) Write a chemical equation to show how temporary hardness is removed by boiling. (1 mark)
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c) State one advantage of hard water. (1 mark)
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16. Find the value of A and B in the following equation.
234 A
X Y
90 B + -1oe (1 mark)
b) A certain radioactive element has a half-life of 6000 years. How long did it take to decay until only 25% of the original amount remained? (2 marks)
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17.Calculate the mass of sulphur which on complete combustion would yield 7dm3 of sulphur (iv)
oxide measured at 182oc and 722 mm Hg pressure.
(0=16, S=32, molar gas volume = 24dm3 at r.t.p) (3 marks) …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
18.The set-up below represents electrolysis of acidified water.
Gas M Gas N
=- - =-=
=- - =-=
=- - - - - - - -= -
Dilute sulphuric acid
d) Write the ionic equation for production of gas
(i) M (1 mark)
(ii) N (1 mark)
c) Why is the above set-up referred to as electrolysis of water? (1 mark)
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19. a) Differentiate between thermo softening and thermosetting plastics. (1 mark)
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b) In the test for the chloride ions in solution, a little nitric acid is added followed by silver nitrate solution, why is nitric acid added. (1 mark)
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20. The set-up below shows laboratory preparation of hydrogen gas, use it to answer the questions that follow.
dilute
sulphuric
acid
Zinc granules Conc. H2SO4
a) Identify two mistakes in the set-up (2 marks)
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b)Why is dilute nitric acid not used in preparation of hydrogen gas. (1 mark)
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21. starting with copper (II) oxide, describe how you can prepare copper (II) sulphate crystals (3 marks)
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22. The set-up below shows the products formed when solid lead (ii) nitrate is heated.
Heat gas y
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-
Lead II Nitrate - -
Crystals-
liquid x ice cold mixture
a) Identify:
(i)Liquid x …………………………………………………………… (1 mark)
(ii) Gas y……………………………………………………………… ( 1 mark)
b) When lead (ii) Nitrate crystals are heated, they descrepitate and decompose, what is meant by the term decrepitating? (1 mark)
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23. Study the set-up below and answer the questions that follow.
Gas x
- -
- -
- -
- - - - - - - - - - - - - - - Chlorine water
- - - - - -- - - - - - - - -
a) Name gas x………………………………………………………………………… ( 1 mark)
b) State the condition which is not indicated on the diagram for gas x to be formed. (1 mark)
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24. a) Aluminium chloride sublimes. Explain why this is possible. (2 marks)
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b) Aluminium is reactive metal yet utensils made of aluminium do not corrode easily.
Explain. (1 mark)
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25. State how burning can be used to differentiate between but-1-yne and butane. (2 marks)
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26. The diagram below represents an incomplete paper chromatogram of pure dyes x, y, z and
mixture w.
Mixture w contains dyes y and z only. Complete the chromatogram to show how mixture w separates (2 marks)
27. a) Give the observation made when ammonia gas is passed over hot platinum wire in the presence of oxygen gas. (1 mark)
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b) Write chemical equation(s) for the reactions taking place in (a) above (2 marks)
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28. a) State and explain the observations made when fluorine gas is bubbled through sodium bromide solution. 2 marks)
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b) When excess ammonia solution is added to a solution of copper (ii) ions, a deep blue solution forms. Write the formula of the complex ions formed. (1 mark)
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29. 22.2cm3 of sodium hydroxide solution containing 4.0g per litre sodium hydroxide were required for complete neutralisation of 0.1g of a dibasic acid. Calculate the relative formula mass of the dibasic acid. (Na = 23, O=16, H=1) (3 marks)
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30 Draw a well labelled diagram showing a set-up for laboratory preparation and collection of dry hydrogen chloride gas. (3 marks)
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