Idea Transcript
NAME:
………………………………………………………… INDEX NO:…………………
SCHOOL:……………………………………………………………………………………………….
233/2 CHEMISTRY PAPER 2 THEORY JULY / AUGUST 2007 2 HOURS
KISUMU DISTRICT JOINT EVALUATION TEST (KDJET) Kenya Certificate Of Secondary Education (KCSE) 233/2 CHEMISTRY PAPER2 THEORY JULY / AUGUST 2007
INSTRUCTIONS TO CANDIDATES Answer all questions in the spaces provided Mathematical tables and electronic calculators may be used All workings must be clearly shown where necessary
For Examiners Use Only Questions
Maximum Score
1
12
2
10
3
10
4
12
5
12
6
13
7
11
TOTAL
80
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Chemistry Practical Tips
Score
2 1. Study the ionization energies in kilojoules per mole and answer the questions below Element
ionization energies in kilojoules per mole 1st
2nd
3rd
4th
5th
6th
A
1,590
2,780
4,700
6,500
8,100
12,500
B
1,010
1,900
4,900
5,000
6,300
7,300
C
940
4,800
6,300
9,180
12,000
16,000
D
1,680
2,010
3,400
10,900
12,400
16,500
(a) (i) Identify the group to which each element belong to:
(2mks)
A B C D (ii) Write the formula of the oxide of D
(1mk)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… (iii) What type of bond will be formed when C reacts with fluorine? Explain
(2mks)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………………………
(b) Use the table below to answer the questions that follow. The table shows the physical properties of elements A, B, C, D and E. The letters do not represent the actual symbols of the elements: Element
Atomic number
Melting point0C
A
11
97.8
B
13
665
C
14
1430
D
17
-101
E
19
64
(i)
Select an element which is: (I)
A poor conductor of electricity.
(1mk)
……………………………………………………………………………………
© KDJET 2007
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(II)
3 The most reactive non-metal.
(1mk)
…………………………………………………………………………………… (ii) To which period of the periodic table does element E belong?
(1mk)
…………………………………………………………………………………………… …………………………………………………………………………………………… (c) Using dots (•) and crosses (X) to represent the outermost electrons show the bonding in the compound formed between elements C and D.
(2mks)
(d) Explain why the melting point of element B is higher than that of element A.
(2mks)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………………………
2. (a) State Hess’s law.
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(b) The heat of combustion of Propane Carbon and Hydrogen are given below. C3 H8 (g) + 5O2(g) C(s) + ½ O2(g) H2(g) + ½ O2(g)
3 CO2(g) + 4H2O(l) ∆ Hθ1 =-2220.1kjmol-1 CO2(g) + H2O(l)
∆ H2 θ = -393.5kjmol-1 ∆ H3θ = -285.8kjmol-1
Write a thermochemical equation to show the formation of propane from its elements.
(i)
(1mk) …………………………………………………………………………………………………… (ii)
Using the information above, show the formation propane using an energy cycle diagram. (2mks)
© KDJET 2007
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4 Calculate the enthalpy of formation of propane.
(iii)
(2mks)
(c) Use the information in the table to answer the questions below. Alkane
Heat of combustion kjmol-1
Methane
8.90 x 102
Ethane
1.56 x 103
Propane
2.22 x 103
Butane
2.877 x 103
Pentane
Predict the heat of combustion of propane.
(i)
(1mk)
……………………………………………………………………………………………………
(ii)
Explain the difference in the molar heat of combustion between the successive alkanes. (1mk)
……………………………………………………………………………………………………… Which of the above alkanes will be the best fuel when their heat value is considered. (C = 12, H= 1)
( 2mks)
……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 3. The flow chart below is a summary of fractional distillation of air.
© KDJET 2007
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5 Explain how Carbon (IV) Oxide gas is removed in step I
(i)
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
State the form in which F is removed.
(ii)
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(iii)
Identify products D and E
(2mks)
D:E:(b) (i) Explain how dust particles are removed in step I
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(ii) Describe how you can distinguish a gas jar of Carbon (II) oxide from Carbon(IV) Oxide. (2mks) …………………………………………………………………………………………………… …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………………………
(iii) Give two commercial uses of Carbon (IV) Oxide gas.
(2mks)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(iv) State one use of substance G
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
Time in minutes © KDJET 2007
Total volume of gas in cm3 233/2
6 4.
0
0
1
220
2
410
3
540
4
620
5
640
6
640
7
640
In an
experiment, 1.0 gram of an alloy of copper and magnesium were reacted with excess 4M Hydrochloric acid, and the gas collected measured at different time intervals. The results were recorded as shown below. (a) Write an equation for the chemical reaction taking place.
(1mk)
……………………………………………………………………………………………………… ……………………………………………………………………………………………………… (b) On the grid provided, plot a graph of the volume of the gas (vertical axis) against time (horizontal axis)
(3mks)
(c) Using the graph, determine: © KDJET 2007
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(i)
7 The rate of reaction at 2 ½ minutes.
(1mk)
(ii)
The volume of the gas at the end of 3 ½ minutes.
(1mk)
(d) The synthesis of ammonia from nitrogen and hydrogen is carried out in the haber process using the equation below. N2(g) +3H2(g)
2NH3(g)
∆Hθ = -92kjmol-1
What information is given by the thermochemical equation above.
(i)
(1mk)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… Explain how an increase in temperature would affect the yield of ammonia.
(ii)
(2mks)
……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… (iii)
Explain how an increase in pressure would affect the equilibrium of the mixture.
(2mks)
……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 5. The scheme below shows several reactions starting with propanol. Study the scheme and answer the questions which follow.
(a) (i) Name gas R © KDJET 2007
(1mk) 233/2
8 ……………………………………………………………………………………………
(ii) Name and draw the structural formular of compound Q.
(2mks)
……………………………..
(iii) What conditions and reagents are necessary to convert S and T.
(2mks)
Reagents:…………………………………………………………………………………… Conditions:……………………………………………………………………………………
Write an equation for the reaction that takes place when equal volumes of chlorine gas
(iv)
reacts with propane.
(1mk)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… (b) The table below shows some properties of the organic compounds U,V and W. Use the information to answer questions that follow. U
V
W
Reaction with
Decolourise bromine No reaction
Decolourises
liquid bromine
very fast
bromine liquid very slowly
Combustion
Burns with yellow
Burns with blue
Burns wit a clear
smoky flame
flame leaving no
yellow flame
residues Rection with con 0
H2SO4 at 180 C (i)
No reaction
It is dehydrated to
No reaction
form compound U
To which homologous series does each compound belong?
(3mks)
U
……………………………………………………………………………………
V
……………………………………………………………………………………
W
……………………………………………………………………………………
(c) The structure below is a polyamide formed from two types of monomers. © KDJET 2007
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9 H
O
│
║
─ N─ (CH2)6 ─ N ─ C ─ (CH2)4 ─ C ─ │
║
H
O
(i)
Draw the structure of the two monomers forming the polyamide above.
(ii)
Give one use of the polyamide above.
(2mks)
(1mk)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… 6. (a) Below are standard electrode potentials for some half cell reactions. Q2+(aq) + 2e-
Q(s)
-0.76V
R2+(aq) +2e-
R(s)
-0.13V
S+(aq) + e-
S(s)
+0.80V
2+
T
(aq)
+ 2e
-
T(s)
+0.34V
The cell below as set up using Q and R electrodes
(i)
Write down half-cell equations of each half-cell.
(2mks)
…………………………………………………………………………………………… …………………………………………………………………………………………… (ii) © KDJET 2007
Write down the overall cell equation.
(1mk) 233/2
10
(iii)
Calculate the e.m.f of the cell above.
(iv)
Explain how the slat bridge helps in maintaining the charge balance in each half-cell when the cell is in operation.
(1mk)
(2mks)
…………………………………………………………………………………………… ……………………………………………………………………………………………
(v)
Explain why potassium chloride salt bridge can not be used when lead nitrate solution is used as an electrolyte in the above setup.
(2mks)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… (b) When an electric current was passed through Copper(II) Nitrate solution, gas N which relights a glowing splint was produced at electrode L
(i) Complete the diagram to show how gas N can be collected
(1mk)
(ii) Write an equation for the formation of the product at the anode.
(1mk)
(iii) © KDJET 2007
What would you observe in the electrolyte at the end of the experiment after passing the 233/2
11 current for along time?
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
Calculate the mass of copper deposited if a constant current of 5 ampheres was passed for
(iv)
3 hours through copper(II) nitrate solution. (Cu =63.5, F =96500 coulombs ) (2mks)
7. (a) Below is a flow chart diagram for the manufacture of sodium carbonate by the Solvay process. Study it and answer the questions that follow.
Name substance N.
(i)
(1mk)
……………………………………………………………………………………………………
Explain the use of water in chamber B.
(ii)
(1mk)
…………………………………………………………………………………………………… …………………………………………………………………………………………………… (iii) © KDJET 2007
Name the two raw materials required in the manufacture of Sodium Carbonate.
(1mk) 233/2
12 …………………………………………………………………………………………………… …………………………………………………………………………………………………… ……………………………………………………………………………………………………
Write an equation for the reaction taking place in chamber C.
(iv)
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(v)
A factory produced 63 tonnes of Sodium Hydrogen Carbonate which is further used to produce Sodium Carbonate. Calculate the number of tonnes of Sodium Carbonate produced assuming the plant is operating at 100% efficiency. (C = 12, O = 16, H = 1 Na = 23.0) (2mks)
(b) (i) Name the ore from which Sodium can be extracted.
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
What is the role of Calcium Chloride in the extraction of Sodium metal from its ore?
(ii)
(1mk) …………………………………………………………………………………………………… ……………………………………………………………………………………………………
(iii)
Sodium metal is normally extracted by the Down’s process. Write equation for the reactions that takes place at the cathode.
(1mk)
…………………………………………………………………………………………………… ……………………………………………………………………………………………………
(iv) Give one use of sodium metal and the by product.
(2mks)
Sodium:……………………………………………………………………………………………
By-product:……………………………………………………………………………………………
© KDJET 2007
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