INSTRUCTIONS TO CANDIDATE
- Write your name and admission number in the spaces provided.
- Sign and write the date of examination in the spaces provided
- Answer all the questions in the spaces provided
- All working must be shown where necessary
- Electronic calculators and mathematical tables may be use.
- Study the information given below and answer the questions that follow.
Element Atomic radius(nm) Ionic radius nm Formula of oxide Melting point(ºc) A 0.364 0.421 A2O -119 D 0.830 0.711 D O2 837 E 0.592 0.485 E2 O3 1466 G 0.381 0.446 G2 O3 242 J 0.762 0.676 J O 1054 - Which elements are non-metals .Give a reason?(2mks)
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- Write a formula of a compound formed when J combines with A(1mk)
- What type of bond exist between J and D.(1mk)
- Explain why the melting point of the oxide of E is higher than that of the oxide of G.(2mks)
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- Which two elements would react with each other most vigorously.Give a reason.(2mks)
- Which element would be suitable for making utensils for boiling water.State two properties that make the elements suitable for the use.(2mks)
- Elements Qand R haveelectronic configuration 2.8.2 and 2.8.6. respectfully.
- Explain why the ionic radius of R is expected to be greater than its atomic radius.(1mk)
- Write the equation for the reaction between Q and R.(1mk)
- The chromatogram below is of and acid enzyme x and y and three simple sugar P,Q and R.
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- Name two simples sugars present in both x and y.(2mks)
- Name lines L and M. (2mks)
L-
M- - What property is exhibitaed by simple sugar x.(1mk)
- Two pieces of paper were lowered into different Bunsen burner flames and removed quickly.The results were as shown below.
- Which paper was lowered into a Bunsen burner whose air hole were closed.Explain(2mks)
- Oxygen can be obtained industrially by fractorise distribution of liquid air
- Why is the gas mixture passed through sodium hydroxide solution.(1mk)
- In the final stage,which gas is distil out fuse.explain.(1mk)
- Name two commercial uses of oxygen gas.(1mk)
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- Study the flow diagram and answer the questions below.
- Identify
- White ppt I (1mk)
- Solution II (1mk)
- Residue II (1mk)
- Write ionic equation for the reactions colourless solution (II) with Pb(NO3) 1mk
- Write observations that would be made when ammonia solution is added drop wise till in excess to the colourless solution(II) 2mks
- Below are PH values of some solutions
Solution Z Y X W PH 6.5 3.5 2.2 7.2 - Which solution is likely to be
- Acidic rain (1mk)
- Potassium hydroxide (1mk)
- A basic substance V reacted with both solutions Y and X.What is the nature of V.(2mks)
- Name two substances that shows this characteristics in question (ii) above.(2mks)
- Which solution is likely to be
- Identify
- A sample of crude oil was heated and its vapour passed over red-hot pumicestore. A mixture of gases was evolved which decolourised bromine in tetra chloromethane and burnt in air with a yellow flame.
- What process id taking place when the vapour from the crude oil passes over heated pumice.(1mk)
- Name the most likely type of compound causing decolourisation of the bromine solution.(1mk)
- Name two compounds formed when the gas mixture above burns in air.(1mk)
- Study the flow chart below and answer the questions that follow.
- Identify substances (4mks)
A-
B-
F-
G- - Write down the equation for the formation of
- Substance C
- E and F
- Gas G
- Substance D was formed to have molecular mass of 42,000 .Determine the number of molecules present in the substances(H+1 ,C=12) 2mks
- State
- The condition necessary for the conversion of ethanol to substance A.(1mk)
- The catalyst required in the conversion of A and B.(1mk)
- Identify substances (4mks)
- Study the flow chart below and answer the questions that follow.
- The table below gives the solubility of hydrated copper(ii) sulphate in mol dm-3 at different temperatures.
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Temperature(º) Solubility mol dm-3 20 8 x 10-2 40 12 x 10-2 60 16 x 10-2 80 22 x 10-2 100 30 x 10-2 - On the grid provided plot a graph of solubility of copper(II) sulphate (vertical axis) against temperature.(3mks
- From the graph ,determinee the mass of copper(II) sulphate deposited when the solution is cooled from 700c to 400.(Molar mass of hydrated copper(ii) sulphate = 250g)
- In an experiment to determine the solubility of sodium chloride ,5.0 cm3 of a saturated solution of sodium chloride weighing 5.35g were placed in a volumetric flask and diluted to a total volume of 250cm3.
25.0 cm3 of the dilute solution of sodium chloride completely reacted with 24.1 cm3 of 0.1 M silver nitrate solution.
Ag No3(aq) + NaCl(aq) Ag Cl(s) + NaNO3(aq)
Calculate;- Moles of silver nitrate in 24.1cm3 of solution.(1mk)
- Moles of sodium chloride in 25.0cm3 of solution.(1mk)
- Moles of sodium chloride in 250cm3 of solution(1mk)
- Mass of sodium chloride in 5.0cm3 of saturated chloride solution (Na=23.0 Cu=35.5) (1mk)
- Mass of water in 5.o cm3 of saturated solution of sodium chloride(1mk)
- The solubility of sodium chloride in g/100 g of water.(2mks)
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- The flow chart below shows some of the processes involved in large scale production of sulphur((vi) acid.
Use it to answer the questions that follow.- Name the process
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- Name substance A.(1mk)
- Write an equation for the process that takes place in the absorption tower.(1mk)
- Vanadium (v) oxide is commonly used catalyst in the process.
- Name another catalyst which can be used for this process.(1mk)
- Give two why reasons vanadium (v) oxide is commonly used catalyst.(2mks)
- Sate and explain the observations made when concentrated sulphuric (vi) acid is added to crystals copper(ii) sulphate in a beaker(2mks)
- The reaction of concentrated sulphuric (vi) acid with sodium chloride produces hydrogen chloride gas.State the property of concentrated sulphuric (vi) acid illustrated in the reaction.(1mk)
- Name two uses of sulphuric (vii) acid.2mks
- The above diagram shows a set up that can be used for industrial manufacture of hydrochloric acid.Study it and answer the questions that follow
- Name
- Produce F
- Substance E
- Explain are application of hydrochloric acid in textile industry.(1mk)
- Hydrochloricb acid was added to iron powder in a test tube and shaken thoroughly to mix to 1cm3 of the resulting solution ,six drops of acqueous solution of ammonia were added .
- State the observation made on adding ammonia solution.(
- Explain the observation sated above and white an ionic equation for the reaction.(2mks)
- Concentrated hydrochloric is 35% pure with density 1.18g/cm3.Calculate it’s concentration in moles per litre..(3mks)
- Name
MARKING SCHEME
-
- A 1/2mk and G 1/2 mk 1mk
The ionic radius is larger 1 mk than the atomic radius implying they gain electrons. - JA2 1mk
Metallic(1mk) - The oxide of E is ionic1mk with a giant ionic structure that requires a lot of energy to break the oxide of G is molecular.(2mks)
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- A and D 1mk
A is a non-metal with the smallest ½mk atomic radius hence most electronegative
D is a metal with the smallest atomic radius hence most electropositive. ½mk - 1mk Has high melting point ½mk and good ½mk conductor of heat being a metal .
- A and D 1mk
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- R gains 2es and hence there is less nuclear 1mk charge /attraction than its atom/gains 2es nuclear attracts 20es against 16 electrons in the atom.
- Q(s) + R(s) → QR(s) 1mk
- A 1/2mk and G 1/2 mk 1mk
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-
- P and Q (2mks)
- L-Baseline (1mk)
M- Solvent front (1mk) - Most sticky/less soluble(1mk)
- B(1mk)
Flame B burns completely because its very hot but A has unburnt region hence it contains unburnt region.91mk) -
- Sodium hydroxide solution absorbs carbon (IV) oxide gas(1mk)
- Nitrogen gas. Because it has the lowest boiling points.(2mks)
- Used in oxyacetylene flame.
- Burning fuels for propelling rockets.
- To remove iron impunities during steel making. Any 2 – 1mk
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-
-
- Zn (OH) 2(g) (1mk)
- Zn CL2(aq) (1mk)
- ZnO(s) (1mk
- 2Cl- (aq) + Pb2+(aq) (1mk)
- White ppt formed (1mk)
Dissolve in excess (1mk) -
- Z (1mk)
- Y (1mk)
- Amphoteric (1mk)
- Zn (OH)2(s) / zinc hydroxide. (1mk)
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- A-Ethane C2 H4 CH2 =CH2
B- Ethane C2 H6 CH3 CH3
F – Carbon (IV) oxide CO2
G- Hydrogen H2 (4mks) -
- C2H(g) + Br2(l) → C2H4Br2or CH2 Br - CH2Br (1mk)
- 2C2 H6(g) + 7O 2(s) → 4CO2(g) + 6H2O (g)
If not balanced = 0mk
Wrong or missing symbols = 1/2mk - 2Na(s) + 2H2 O(l) → 2NaOH9aq) + H2(g) (2mks)
Balanced = 2mks
Not balanced =0mk.
- Mass of monomer = 2(12 + 2)= 28
No.of molecules = 42000 = 15000 molecules (2mks)
28 -
- ..Temperature of 180º c (1mk)
- Nickel catalyst (1mk)
- A-Ethane C2 H4 CH2 =CH2
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-
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- scale(I)
- Plotting all points correctly (I)
- Curve (shape)
- 0.188- 0.12 = 0.068 mol(I)
Therefore mass of hydrated copper(II) sulphate
= 0.68 x 250 = 17g
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- Moles of AgNO3 = 0.1 x 24.1 = 2.41 10-3
1000 - Moles of NaCI = Moles of AgNO3
= 241 x 10 -3 - Moles of NaCL in 250cm3 = 2.41 x 10-3 x 250
25
=2.41 x 10-2 - R.F.M Na CI = 23 + 35 .5 = 58.5
Mass of NaCl in 5cm3 = 2.41 x 10-2 x 58.5
= 1.41g - Mass of water = 5.35 – 1.41
= 3.94g - vi.3.94 of water contains 1.41g of NaCl
100 g of water = 1.41 x 100
3.94
=35.7
- Moles of AgNO3 = 0.1 x 24.1 = 2.41 10-3
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- Contact process=1mk
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- Sulphuric(IV) acid.(1mk)
- H2 SO 4(aq( SO 3(g) H 2 S 2 O7(l)
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- Platinized asbestos (1mk)
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- It is not highly poisoned(2mks)
- It is cheap
- Crystals turn blue to white .Concentrated sulphuric(IV) acid removes water of crystals from hydrated copper(II) sulphate.(2mks)
- Concentrated sulphuric (VI) acid is less volatile hence displaces more volatile acids from their salts.(1mk)
- Used in;
- accumulators.
- in manufacture of fertilizers.
- in etching of metals.
- in manufacture of detergents.(any 2mks)
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- Hydrogen chloride gas (HCL (g) 1mk
- Water (H2O (l) 1mk
- ……………………………..
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- Green ppt(1mk)
- Insoluble iron (II) hydroxide was formed(1mk)
Fe2+(aq) + 2OH (aq) Fe(OH)2(s) 1mk
- Mass of 1000cm3 of solution = 1000 x 1.18 ½mk
= 1180g ½mk
Mass of HCl = 35 x 1180 ½ mk
100
= 413g ½ mk
Molarity = 413 ½ mk
36.5
= 11.3151 M ½mk
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