INSTRUCTIONS TO CANDIDATES
- Write your NAME and INDEX NUMBER in the space provided above
- Sign and write the date of examination in the spaces providedabove
- Answer ALL the questions in the spaces provided
- ALL working must be clearly shown where necessary.
- Mathematical tables and silent electronic calculators may be used.
FOR EXAMINER’S USE ONLY
Question | Maximum score | Candidate’s score |
1 -31 | 80 |
|
Total score | 80 |
|

QUESTIONS
- An element K has atomic number 20 while element M has atomic number 8.
- Write the electronic configuration for K and M
K ………………………………………………………………………………………….. 1mark
M....………………………………………………………………………………….……. 1mark - Write the symbol of the most stable ion of K and M
K…………………………………………………………………………………………. 1mark
M…………………………………………………………………………………………. 1mark
- Write the electronic configuration for K and M
- Molten Lead (II) bromide is electrolyzed using carbon electrodes. Write the half equations of the reactions that occur at the anode and the cathode.
- Anode…………………………………………………………………………………….…… 1mark
- Cathode……………………………………………………………...……….………………… 1mark
- Explain why the conductivity of metals decreases with increase in temperature. 2marks
........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................ - Three metal oxides XO, YO, and ZO are heated with powdered metal Y. Hot powdered Y will remove oxygen from XO but not from ZO. Arrange the metals in order of reactivity, starting with the most reactive. 1mark
................................................................................................................................................................................................................................................................................................................................................ - Some sodium chloride was found to be contaminated with copper (II) oxide. Describe how a sample of sodium chloride can be separated from the mixture. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Hot platinum wire was lowered into a flask containing concentrated ammonia solution as shown below.
State and explain the observations made. 3marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - The set up below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are 80ºC and 110ºC.
- Name B………………………………………………………………………………….. 1mark
- What is the purpose of the thermometer 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Which liquid was collected in the test tube? 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Draw a dot (.) and cross (x) diagram to show bonding in carbon (II) oxide. 2marks
- Ammonium nitrate was gently heated and the products collected as shown in the diagram.
- Identify:
- Colourless liquid H………………………………………………………………………………………… 1mark
- Gas G………………………………………………………………………………………… 1mark
- Describe one physical and one chemical test that can be used to identify gas G. 2marks
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Identify:
- Air was passed through several reagents as shown in the flow chart below.
- What is the purpose of concentrated potassium hydroxide solution? 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………. - Write an equation for the reaction which takes place in the chamber with magnesium powder. 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….. - Name one gas which escapes from the chamber containing magnesium powder.
………………………………………………………………………………………………………………………..
Give a reason for your answer 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….
- What is the purpose of concentrated potassium hydroxide solution? 1mark
- Name the following substances.
- CH2 CH CH2 CH3 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - CH3 CH CH CH2 CH3 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- CH2 CH CH2 CH3 1mark
- The diagram below shows the acidic and basic oxides fit into the general family of oxides.
- State the name given to the type of oxide that would be placed in the shaded area. 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Give the name of any oxide that would be placed in the shaded area. 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- State the name given to the type of oxide that would be placed in the shaded area. 1mark
- Study the information in the table below and answer the questions that follow. The letters do not represent the actual symbols of the elements.
Substance
Solubility in water
Electrical conductivity
Solid
Molten
A
Insoluble
Good
Good
B
Soluble
Poor
Good
C
Insoluble
Poor
Poor
- Which of the substances is highly likely to be sodium chloride? Explain 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - What type of bond exists in substance A? 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - State a possible structure in substance C? 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Which of the substances is highly likely to be sodium chloride? Explain 2marks
- Laboratory results showed the composition of a compound to be 58.81% barium, 13.72%, sulphur and 27.47% Oxygen. Calculate the empirical formula of the compound. Ba=137, S = 32, O = 16. 2marks
- The diagram below shows a wooden splint that was placed horizontally across the middle part of a non-luminous flame.
- Explain the observation made 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Explain why non-luminous flame is preferred for heating than the luminous flame. 2marks
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Explain the observation made 2marks
- 200cm3 of oxygen gas took 60 seconds to diffuse through a porous plug. Determine the time taken by 300cm3 of sulphur (IV) oxide to diffuse through the same plug under the same conditions.
(O=16, S = 32) 3marks - Explain why?
- Both methane and diamond are covalently bonded. Methane is a gas but diamond is a solid with very high melting point. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Ammonia is dissolved in water using an inverted funnel. 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Both methane and diamond are covalently bonded. Methane is a gas but diamond is a solid with very high melting point. 2marks
- Explain giving reasons why?
- Sulphuric acid is not used with marble in the preparation of carbon (IV) oxide 2marks
…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..………………….. - Water cannot be used to distinguish oil fire. 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Sulphuric acid is not used with marble in the preparation of carbon (IV) oxide 2marks
- A gas occupies 4dm3 at -23ºC and 152 mmHg. At what pressure will its volume be halved, if the temperature then is 227ºC.? 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… -
- Sodium, Magnesium and Aluminium are elements in the periodic table. Explain why aluminium has a higher melting and boiling point than sodium and magnesium. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - The ionization energy of an atom is strongly influenced by three atomic parameters. State two of these parameters. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Sodium, Magnesium and Aluminium are elements in the periodic table. Explain why aluminium has a higher melting and boiling point than sodium and magnesium. 2marks
- 15cm3 of a solution containing 2.88g/dm3 of an alkali XOH completely reacts with 20cm3 of 0.045M sulphuric acid. Calculate the molarity and relative atomic mass of X present in the alkali. 3marks
- Describe how a solid sample of calcium sulphate can be prepared using the following reagents; dilute nitric (v)acid, dilute sulphuric (vi) acid and solid calcium carbonate 4marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Crude oil is the main source of organic compounds such as hydrocarbons. The hydrocarbons in the crude oil have to be separated.
- Name two important hydrocarbons obtained from crude oil. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Give the uses of the two hydrocarbons named in (a) above. 2marks
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Name two important hydrocarbons obtained from crude oil. 2marks
- A hydrocarbon Q was found to decolourise potassium manganate (vii) solution. When two moles of Q were burnt completely six moles of carbon (iv) oxide and six moles of water were formed.
- Write the structural formula of Q. 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………........................................................................................................................................................................ - Name the homologous series to which Q belongs 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Write the structural formula of Q. 1mark
- Dilute sulphuric acid was added to a compound X, of magnesium. The solid reacted with the acid to form a colourless solution, Y and a colourless gas Z which formed a white precipitate when bubbled through lime water.
Name:-- Compound X 1mark
……………………………………………………………………………………………………………… - Solution Y 1mark
……………………………………………………………………………………………………………… - Colourless gas Z 1mark
………………………………………………………………………………………………………………
- Compound X 1mark
- When dry hydrogen gas passed over heated Lead (II) oxide in combustion tube, a grey solid was formed.
- Identify the grey solid. 1mark
…………………………………………………………………………………………………………. - Write the equation of the reaction taking place in the combustion tube. 1mark
…………………………………………………………………………………………………………………................................................................................................................................................................... - Write the equation involving the blue flame. 2marks
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - What do (C F C’ S) mean? 1mark
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- Identify the grey solid. 1mark
-
- What is meant by the term allotrophy? 1mark
……………………………………………………………………………………………………………………………………………………………………………………………………………………………… - Explain in terms of structure and bonding why graphite is soft with greasy feeling. 2marks
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
- What is meant by the term allotrophy? 1mark

MARKING SCHEME
-
- 20K 2.8.8.2 1mk
8M 2.6. 1 mk
Loose - K 2.8.8.2 → K2+ 1 mk
2e
Gain
M 2.6 → M2- 1 mk
2ē
- 20K 2.8.8.2 1mk
-
- Anode
2Br-(l) → Br2(g) + 2ē Balmk
S.S 1 mk - Cathode
Pb(l)2+ + 2ē → Pb(s) 1 mk
- Anode
- Increase in temperature increases the kinetic energy of positive centres (nucleous) and the electrons making positive centres and electrons to vibrate more. 1 mk
This increases the collisions between the positive centres and electrons increasing resistance of the metal hence decreasing conductivity. 1 mk - → Z Y X 1 mk
Decreasing order - Add water to the mixture and stir to dissolve sodium chloride leaving copper (ii) oxide which is insoluble. 1 mk
Filters to remove copper (ii) oxide as residue and sodium chloride as filtrate ½ mk
Evaporate the filtrate to obtain sodium chloride crystals. ½ mk -
- Hot platinum wire glows red. ½ mk
- Brown fumes are observed ½ mk
Explanation
Reaction between oxygen gas and ammonia over platinum wire is exothermic 1 mk
Ammonia is oxidized in presence of platinum catalyst to produce nitrogen (ii) oxide (½ mk) which is further oxidized to nitrogen (iv) oxide. ½ mk
-
- B- Lie berg condenser.1mk
- Thermometer – To maintain the temperature for distillation. 1mk
- Liquid C1mk
2mks
-
-
- Liquid H = Water 1mk
- G - Nitrogen (i) oxide 1mk
- Physical test- Test the boiling point and melting point.
Boiling point should be 100ºC and melting point 0ºC at sea level Any 1 x 1 = 1mk
Chemical test- Turns white anhydrous copper (ii) sulphate to blue. 1mk
Turns blue anhydrous cobalt (ii) chloride to pink. Any 1 x 1 = 1mk
-
-
- Remove / absorb carbon (iv) oxide 1mk
- 3Mg(s)+ N2(g) Heat → Mg3 N2(s) 1mk
- Neon / Argon 1mk
Are inert gases / unreactive gases and therefore do not react with magnesium. 1mk
-
- But - I - ene 1mk
- Pent – 2 – ene 1mk
-
- Amphoteric oxide 1mk
- Lead (ii) oxide / Zinc oxide / Aluminium (iii) oxide 1mk (Ignore formula)
-
- B 1mk
Sodium chloride is soluble in water since its ionic and do not conduct electricity in solid state but conducts electricity in molten state. 1mk - Metallic bond 1mk
- Giant atomic / covalent structure 1mk
- B 1mk
-
Element Ba S O % Composition 58.81 13.72 24.47 RAM 137.0 32.0 16.0 No. of Moles 58.81 13.72 24.47 137 32 16 ½ mk = 0.4293 0.4281 1.7168 Simplest ratio 0.4293 0.4281 1.7168 0.4281 0.4281 0.4281 ½ mk 1 : 1 : 4 E.F = BaSO4 1mk
-
- The outer part (zone) has complete combustion and hence hotter than middle zone forming a charred black part.1mk
Middle part (zone) has incomplete combustion and hence less hot forming unburnt part.1mk - Non-luminousflameis hotter thanluminousflame 1mk
Non luminous flame does not produce soot. 1mk
- The outer part (zone) has complete combustion and hence hotter than middle zone forming a charred black part.1mk
- Ro2= 200 = 64
RSo2 60 1mk32
300
t
= 200 x t = 2
60 300
30
= t = 2 x60 x 31mk
2
= 1.41 x 90
= 127.26sec 1mk -
- Methane molecules are held together by weak molecular force of attraction½mk (VanderWaals force) which requires less energy to break / overcome giving methane low B.P.½ mk
Diamond – each carbon atom is bonded to 4 other carbon atoms through very strong½ mk covalent bonds which require a lot of energy to break/overcome giving diamond a very high B.P½ mk - Ammonia is highly soluble in water and inverted funnel prevents sucking back½ mk and also creates a large surface area for absorption. ½ mk
- Methane molecules are held together by weak molecular force of attraction½mk (VanderWaals force) which requires less energy to break / overcome giving methane low B.P.½ mk
-
- Sulphuric acid reacts with marble (calcium carbonate) forming insoluble calcium sulphate ½ mk which forma a coating over marble stopping any further reaction. ½ mk
- Oil is less dense½ mk than water making oil to float½ mk on top hence continues to burn.
- V1 = 4dm3, P1 = 152mmHg ; T1 = -23ºC
V2 = 2dm3 P2 = ? T2 = 227ºC
T1 = -230C + 273 = 250k
T2 = 227 + 273 = 500kP1V1 = P2V2
T1 T2152 x 4 = P2 x 2
250 500 1mk1
2
P2 = 152 x 4x 500
250 2
1 1 = 608mmHg 1mk - Aluminium has more delocalized (½ mk) valency electrons hence stronger metallic (½ mk) bonding which requires more energy to break / overcome.
Sodium and magnesium has few delocalized ( ½ mk)valency electrons hence weaker metallic ( ½ mk) bonding which requires less energy to break /overcome. - Size of the atom / number of energy levels 1mk
Atomic number / number of protons 1mk
Shielding effect 1mk any 2 x 1 = 2mks
- Aluminium has more delocalized (½ mk) valency electrons hence stronger metallic (½ mk) bonding which requires more energy to break / overcome.
- 2XOH(aq) + H2SO4(aq) X2SO4(aq) + 2H2O(l)
15cm3 20cm3
M=? 0.045mXOH = 2 = 15 x M
H2SO4 1 20 x 0.045 ½ mkTherefore M = 2 x 20 x0.045 = 0.12moles / L ½ mk
1 x 15
0.12moles / L has 2.88g/L
1 mole = ?
= 2.88 = 24 ½ mk
0.12
RFM = 24 ½ mk
XOH = 24
X + 16+1 = 24
X =24 - 17 = 7 RAM of x = 7 1mk - Calcium carbonate is reacted with dilute nitric acid to form ½ mk calcium nitrate, carbon (iv) oxide and water.
- CaCO3(g) + 2HNO3(aq) = Ca(NO3)2 (aq) + CO2(g) + H2O(l) ½ mk
- Calcium nitrate is then reacted with dilute sulphuric acid to form calcium sulphate and nitric acid.
- Ca(NO3)(aq) + H2SO4(aq) = CaSO4 (aq) + 2HNO3(aq) ½ mk
- Filtration is then done to obtain calcium sulphate as residue.
- The residue is washed with distilled water and dried in the sun or between filter paper.
-
-
- kerosene
- Diesel
- Petrol
- Gasoline Any 2 x 1 = 2mks
-
- Kerosene – used for cooking1mk
- Diesel – used for diesel engine1mk
- Petrol – used for petrol engine1mk
- Gasoline – used for jet fuel. 1mk Any 2 x 1 = 2mks
-
-
- 2Cx Hy → YCO2 + YH2O
X = 6 = 3
2
Y = 12 = 6
3
M.F.= C3H6 ½ mk
Structural formula =½ mk
- Alkenes
- 2Cx Hy → YCO2 + YH2O
-
- X – Magnesium carbonate 1mk
- Y – Magnesium Sulphate 1mk
- Z – Carbon (iv) oxide 1mk
-
- Grey solid – Lead metal 1mk
- PbO(s) + H2(g) Heat Pb(s) + H2O (l)1mk
- 2H2(g) + O2(g) 2H2O(g) 2mks
- CFC’s – Chlorofluoro carbons 1mk
-
- Allotrophy – is the existence of a substance in different forms without change of physical state / existence of an element in more than one form in the same physical state. 1mk
- Graphite - Each carbon atom is bonded to 3 other carbon atoms forming hexagonal layers which are held together by weak Vander Waals force enabling the layers to slide / slip along each other making graphite soft/ greasy. 2mks
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