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KCSE CLUSTER TESTS 27

Chemistry Paper 2

1.

1(a) E (1mrk)
Its ions have the greatest tendency to accept electrons // Has the highest positive electrode potential // Ions
are strongest oxidizing agent

(ii) NB: The arrow should be on the wire or electrode but not outside the diagram.
(iii).To complete the circuit // maintain change balance // replace ions used up in half cells. (1mrk)
C (i) OH- ions migrate to the anode(1mrk). OH- ions are preferentially discharged to form O2 gas. // OH- ions oxidized to form O2 (g)(1mrk)

(ii) Copper anode dissolves to give Cu2+(aq) // Copper anode is oxidized (1mrk) this is because oxidation of copper requires lesser energy than oxidation of OH-

13 marks

2.

(a) (i) Dehydration (1mrk)

(ii) Warm // Heat½ // presence of Conc.H2SO4½
(iii) Chloro-ethene
(iv) Ethanol / CH3CH2OH(l)

(b) (i) C2H4O2 ½ it has a melting point of 289.6K which is higher than 283.0K½
(ii) C3H8O is more soluble in water than C5H12.This is because C3H8O hydrogen bonds which improves it solubility while C5H12 does not hydrogen bond

13 marks

3.

.(a)(i) On the grid [ period 3 and group 4]

(ii) L (1mrk). Atomic radius decreases across a period from left to right // The nuclear charge or no. of protons increase across the period hence electrons are strongly attracted towards nuclear

b) Q is more reactive with sodium than R.(1mrk) This is because. Q has a higher tendency to accept electrons
than R// Q is more electronegative than R

d). In bulbs to provide an inert atmosphere so as to minimize the rate of oxidation of filament. (mrk

11 marks

4.

(ii) The amount of heat given out when one mole of a substance is completely burnt in excess oxygen at standard conditions

(iii)Heating value is – 40.32 kilo joules.// the heat given out when 1g of butane is burnt.

11 marks

5.

a)(i) To remove the metal oxide layer which interfere with reaction

b).(i) Graph:
-Labeling and axis (correct) – (1mrk)
- Plotting [all points correct] – (1mrk)
- Smooth Curve – (1mrk)

12 marks

6.

ii) – In treatment of drinking water
-Manufacture of chloroform aneasthetic
-Manufacture of germicide, fungicides and pestcides

11 marks

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