Chemistry Paper 2 Marking Scheme
KCSE CLUSTER TEST 14
Chemistry Paper 2
(a) (i) Ethene
(ii) It is insoluble in water.1 2
(b) (i) Polyethene.
(ii) It is non-biodegradablecauses land pollution. 1
(c) (i) Fractional distillation.1
(ii) Alkanes.1 2
(d) (i) Cracking of alkanes.1
(ii) -Bubble each through bromine;(ii) -Bubble each through bromine; C3H8 does not decolourize½ Br2 whileC3H6 decolourizes//½ or 3 -Use acidified potassium manganate (vii);C3H8 does not decolourize.½ while C3H8 does not decolourize½ 2 Br while C3H6 decolourizes//½ or 3 -Use acidified potassium manganate (vii); C3H8 does not decolourize.½ while
C3H6 decolourize.½
12 marks
(a) V,Y and Z. Any 2(½mk each)
They are metals//Have delocalized electrons.1
(b) (i) V,X and Y.
(ii) V and Z .1 2 mentioned award ½ mk
Its B.P is below room temperature/ 250
(ii) W .½.
It is inert.½
(e) (i) Ionic//Electrovalent.
(ii) Giant atomic//Giant covalent structure
(f) (i) Oxygen..1
(ii) Hydrogen..1
12 marks
(a) The heat change that occur when a given mass of a substance changes from solid to liquid at melting point.1
(b) (i) -Enthalpy of combustion of carbon.1
-Enthalpy of formation of carbon(iv)oxide1
iv)
12 marks
(a) (i) -electrolysis of brine.1 Or Cracking of alkanes.
(ii) Fractional distillation of liquid air1
(b) Temperature of C 0450 .1 Pressure of 200 atmosphere.1
(c) Step I-Finely divided Iron.1 Step II- Platinum rhodium catalyst.1
(d) (i) Copper metal.1 (ii) Ammonium Nitrates.1
12 marks
(a) (i) -Gain of electrons or –Decrease in oxidation state.
-Removal of oxygen from a compound
-Chemical addition of hydrogen.
(ii) Apparent charge assigned to an element in compound form, free element or Ion.
b)
(ii) Colour turns from blue to½ colourless. CU2+ ions reduced½ to . Cu
(iii) Electroplating, metals purification, extraction of metals, mft of . NaOH Any one
12 marks
a)
Penalize ½mk for wrong or missing symbols.
12 marks
(i) Solvay process.1
(ii) Sodium carbonate.1
(iii) J=Calcium Carbonate.1
K=Sodium hydrogen carbonate.1
Q=Calcium Oxide.1
(v) -Preparation of aerated drinks1 -Preparation of dry ice.1
(b) (i) Because low temperature make combustion of fuels incomplete.1
(ii) -Melting of Polar-ice caps causing rise in sea level.v1
-Erratic weather patterns.
11 marks