Questions
Instructions to the candidates:
 Answer all the questions
 Mathematical tables and electronic calculators may be used.
 All working MUST be clearly shown where necessary.
 Use the first 15 minutes of the 2 ¼ hours to ascertain you have all the chemicals and apparatus that you may need.
QUESTION 1
 You are provided with solution K and L
 Solution K is 1M H_{2}SO_{4}
 Solution L contains 8.7g of the hydroxide of metal M {with formulae MOH] in 600cm^{3} of the solution
 You are required to carry out the experiment to determine;
 Concentration of solution L
 R.A.M of metal M
Procedure
 Measure 75cm^{3} of solution K and put into a clean 250cm^{3} volumetric flask and add distilled water up to the mark
label this solution W  Fill a clean burette with solution W
 Pipette 25cm^{3} of solution L into a clean conical flask and add 2 drops of phenolphthalein indicator
 Titrate the solution W in the burette against solution L in the conical flask and record the results in the table below
 Repeat {3} and {4} above as you fill the table below.
TABLE 1
I  II  III  
Final burette reading {cm^{3}}  
Initial burette reading {cm^{3}}  
Volume of solution W used {cm^{3}} 
[4mks]
 Calculate the;
 Average volume of solution W used [1mk]
 Concentration of solution W [1mk]
 Number of moles of solution W that reacted with each 25cm^{3} portion of solution L {2mks]
 Calculate the;
 Number of moles of the metal hydroxide {MOH} in solution L that reacted with each portion of solution W [2mks]
 Concentration of solution L [1mk]
 Number of moles of the metal hydroxide [MOH]in 600cm^{3} of solution L [2mks]
 R.A.M of metal M [2mks]
[0=16, H=1]
QUESTION 2
You are provided with solution N and P
 Solution N is 2M HCl
 Solution P is 0.16M sodium thiosulphate
 You are required to carry out the experiment below to determine how concentration affects the rate of reaction between HCl and sodium thiosulphate solutions
PROCEDURE
 Fill a clean burette with solution P.
 Measure 25cm^{3} of the solution P from the burette into a clean 100cm^{3} glass beaker and place on a white piece of paper with a cross[x] marked on it
 Add 10cm^{3} of solution N into it and immediately start a stop watch and note the time taken for the cross beneath the mixture to become invisible
 Clean the 100cm^{3} beaker and measure into it 20cm^{3} of solution P form the burette, and add 5cm^{3} of distilled water into the solution solution
 Repeat step [2] above and note the time taken for the cross to become invisible
 Repeat the experiment using volumes indicated on the table below and as you record the results
TABLE 2
Expt  1  2  3  4  5 
Volume of solution p(cm^{3})  25  20  15  10  5 
Volume of water added to solution p{cm^{3}}  0  5  10  15  20 
Volume of solution N  10  10  10  10  10 
Time taken for the cross to become invisible [in seconds]  
1/t S1 
(4mks)
 plot a graph of 1/t against volume of solution P on the grid provided [3mk]
 From the graph
 Determine the time taken for the cross to become invisible when 12.5cm^{3} of solution P is used [2mks]
 Explain the effect of concentration on the rate of reaction between HCl and sodium thiosulphate solution [2mks]
QUESTION 3
 You are provided with solids Q and R
 You are required to carry out the tests below as you record your observations and inferences
 SOLID Q
Add about 5cm3 of distilled water to solid Q, shake the mixture thoroughly for a while and then filter it
NOTE: Retain both the filtrate and the residue for the tests below
 SOLID Q
TEST  OBSERVATION  INFERENCES  
A  i  Divide the filtrate into 4 portion To the first portion, add 4 drops of NaOH 

ii  Scoop the 2nd portion on a metallic spatula and ignite on a nonluminous flame 

iii  To the 3rd portion, add 2 drops of Pb{NO_{3}}[aq]  
iv  To the 4th portion ,add acidified KmnO_{4}  
B  i  Put the residue in a test tube and add about 2cm^{3} of HNO_{3}  
ii  To the mixture in b{i} above, add 2 drops of KI solution  
ii  SOLID R  
TEST  OBSERVATION  INFERENCES  
A  i  Scoop a portion of solid R on a Metallic spatula and burn on a Nonluminous flame 

B  i  Put the remaining portion of solid R into a clean test tube and add about 3cm^{3} of distilled water, shake and divide into 2 portions 

ii  To the 1st portion, add 2 drops of acidified KMnO_{4} and warm  
iii  To the 2nd portion add NaCO_{3} 
Confidential
 Each student should be supplied with the following
 Burette
 Pipette
 Pipette filler
 Filter funnel
 White tile
 Clamp and stand
 2 conical flask
 100cm^{3} glass Beaker (empty)
 Stop watch
 100cm^{3} measuring cylinder
 10cm^{3} measuring cylinder
 250cm^{3} volumetric flask
 Metallic spatula
 6 clean test tubes
 Test tube holder
 500ml distilled water
 White piece of paper or filter paper
 1 filter paper
 1 labelling paper
 Phenolphthalein indicator
 About 90cm^{3} solution K
 About 100cm^{3} solution L
 About 70cm^{3} solution N
 About 90cm^{3} solution P
 About 0.5gNaHCO_{3}
 About 1.0g solid Q
 About 0.5g solid R
 Each student should have access to the following solutions:
 Mean of heating
 2M NaOH
 2M HNO_{3}
 Pb(NO_{3})
 Acidified KMNO_{4}
 Potassium iodide solution
NB: the above solutions should be supplied with a dropper each.
 SOLUTIONS PREPARATION AND SOLID MEASUREMENTS
 SOLUTION K IS 1M H_{2}SO_{4}
 SOLUTION L IS 0.36 M NaOH CONTAINING 14.4g OF NAOH IN 1 LITRE OF THE SOLUTION
 SOLUTION N IS 2M HCl
 SOLUTION P IS 0.16 M Na_{2}S_{2}O_{3}(SODIUM THIOSULPHATE)
 SOLID Q IS A MIXTURE OF SODIUM SULPHITE(Na_{2}SO_{3}) AND LEAD (II) CARBONATE (PbCO_{3}) MIXED IN THE RATIO 1:1 (should be thoroughly mixed)
 SOLID R IS MALEIC ACID
Marking Scheme
QUESTION 1
TABLE 1
 complete table CT 1 mk
 decimal point D 1 mk
 accuracy A (tied to school value)1 mk
 principal of averaging 1 mk

 Average volume / final accuracy 1(tied to school value)
NB theoretically expected value = 15.0 cm^{3}  1M x 75 cm^{3} ½ mk
250cm^{3}
= 0.3M ½ mk  Ans in (ii)above X ans in (i)above½ mk = ans ½ mk
1000
2MOH_{(aq)} + H_{2}SO_{4 (aq)} → M_{2}SO_{4(aq)} + H_{2}O_{(l)} 1mk
Mole ratio = 2:1 ½ mk
 Average volume / final accuracy 1(tied to school value)

 Moles of solution W = 2 x ans in a(iii) ½ mk
 ans in b(i)x 1000½ mk = ans ½mk
25  ans in (i)x 600 = ans½ mk
25½ mk  8.7/½ mk= RFM OF MOH½ mk
ans in b (iii)
RAM of metal M = RFM (16+1) ½ mk= ans½ mk
QUESTION 2
TABLE 2
 complete table CT1mk
 decimal point D 1mk
 trend (increasing time )1mk
 1/t row completed 1mk
 Graph
Plotting 1mk
Scale 1mk
Straight line touching origin (0,0) 1mk  Correctly read value from the graph 1mk
 Correct reciprocal of value read from the graph 1mk
 Rate at reaction increase with increase in concentration of the sodium thiosulphate because increase in concentration increases number of successfulcollisions
QUESTION 3
 Solid Q

Observation inferences A i No white ppt formed ½ mk Ca^{2+} Mg^{2+}, Pb^{2+}, Al^{3+} Zn^{2+} Absent ii Burns with a golden yellow flame Na+ confirmed iii White ppt formed ½ mk Cl, SO_{4}^{2}, SO_{3}^{2},CO_{3}^{2}1mk iv KMNO_{4} decolorized½ mk SO_{3}^{2}, Confirmed1mk B i Effervescence occurs ½ mk CO_{3}^{2}, SO_{3}^{2}1mk ii Yellow ppt formed½ mk
Pb^{2+} confirmed1mk


 Solid R
Observation inferences A Burns with a yellow sooty flame½ mk =C = C = , = C = C B i Dissolves½ mk forming a colorless solution½ Polar substance½ mk ii KMNO_{4} decolorized½ mk ROH, =C = C =, = C = C = ii Effervescence½ mk H+ or RCOOH1mk
 Solid R
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