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KCSE CHEMISTRY PAPER  3 PREDICTION QUESTIONS AND ANSWERS, KNEC REPORTS (KCSE PAST PAPERS LEAKAGE); GET ALL KCSE 2021-2022 CHEMISTRY PAPER 3 PREDICTION SETS DERIVED FROM TOP NATIONAL MOCKS AND KCSE PAST PAPERS

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KCSE CHEMISTRY PAPER  3 PREDICTION QUESTIONS AND ANSWERS, KNEC REPORTS (KCSE PAST PAPERS LEAKAGE); GET ALL KCSE 2021-2022 CHEMISTRY PAPER 3 PREDICTION SETS DERIVED FROM TOP NATIONAL MOCKS AND KCSE PAST PAPERS

 

KCSE CHEMISTRY PAPER 3 LEAKAGE DETAILS:
POLITE NOTICE: KINDLY NOTE THAT THE KCSE 2021-2022 CHEMISTRY PAPER 3 LEAKAGE IN CIRCULATION IS FAKE. THE CABINET SECRETARY IN CHARGE OF EDUCATION CONFIRMED THAT THE UNIVERSITY STUDENT WHO WAS DISSEMINATING MISLEADING KCSE CHEMISTRY PAPER 3 EXAM PAPERS HAS BEEN DETAINED AND IS AWAITING TRIAL.

Chemistry paper 3 is compulsory for most KCSE Knec-registered candidates. The paper carries a maximum of 40 marks and it contains three major sections made up of three questions– All the three questions are compulsory. The candidate should attempt all the questions in Chemistry paper 3. Question one carries a maximum of 19 marks, question two 12 marks and question 3 09 marks.

This is a hands-on exam that requires the physical involvement of the candidate in practical exams.

The candidates are expected to set apparatus, follow the procedures given to do the practicals, make observations, record them and interpret the results and values arrived at.

KCSE Chemistry paper three generally tests the candidate’s ability to make correct observations and interpret-infer their meaning.

HERE IS A FULL SET OF KCSE CHEMISTRY PAPER 3 PREDICTION QUESTIONS AND ANSWERS; TOP NATIONAL MOCKS & KCSE PAST PAPERS

CLICK ON THE LINKS BELOW TO ACCESS KCSE REVISION MATERIALS FOR CHEMISTRY PAPER THREE

Chemistry-Paper-3-KCSE-2020-Exam

Chemistry-Paper-3-KCSE-2020-Exam

2021-2022 KCSE Chemistry Paper Three  Prediction Questions and Answers, Leakage Details: Emerging Trends in the setting and the marking of chemistry KCSE Paper three. 

BELOW IS A SAMPLE OF CHEMISTRY PAPER 3 EXAMINATION QUESTIONS AND POSSIBLE ANSWERS.

KCSE CLUSTER TESTS 3

Chemistry Paper 3

1.

You are required to find the percentage purity of a sample of sodium carbonate, Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

FA1 contains 4.50 g dm-3 of the impure sodium carbonate.

FA2 is 0.50 mol dm-3 hydrochloric acid, HC1.
(a) Dilution of FA2

By using a burette, measure 34.00 cm3 of FA2 into the 250 cm3 graduated flask (volumetric flask) labeled FA3.

Make up the contents of the flask to the 250 cm3 mark with distilled water.

Place the stopper in the flask and mix the contents thoroughly by slowly inverting the flask a number of times.
Titration

Fill a second burette with FA3, the diluted solution of hydrochloric acid.

25.0 cm3 of FA1 into a conical flask. Add a few drops of methyl orange indicator and titrate with FA3.

Perform one titration and two further titrations to obtain accurate results

Record your titration results in the table below Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

b) From your titration results obtain a suitable volume of FA3 to be used in your calculations.

Show clearly how you obtained this volume. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………….

Calculations

Show your working and appropriate significant figures in all of your calculations.

c) (i) Calculate how many moles of HCl are contained in the FA2 run into the graduated flask(volumetric flask). ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

(ii) Calculate how many moles of HCl are contained in the volume of FA3 which reacted with 25.0 cm3 of FA1 ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

(iii) Use this answer in (c)(ii) to calculate how many moles of sodium carbonate, Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3, are present in 1.00 dm3 of FA1.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………

……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

(iv) Calculate the mass of sodium carbonate, Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3 in 1.00 dm3 of FA1. (C=12.0; O=16.0;Na=23.0) ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

(v) Calculate, to 3 significant figures, the percentage purity of the sodium carbonate,Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3 , dissolved in FA1. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

 14 marks

2.

You are provided with the following reagents.

√FB1 1 mol dm-3 sulphuric acid,Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

√FB2, 0.1 mol dm-3 potassium iodide, KI

√FB3, 0.1 mol dm-3 sodium thiosulphate,Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3;

√FB4, 0.1 mol dm-3 hydrogen peroxide, Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

√ Start solution √Distilled water. In the presence of an acid, iodide ions are oxidised by hydrogen peroxide to iodine.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

The rate of reaction can be followed by timing the formation of a fixed amount of iodine in the solution. If sodium thiosulphate is present in the reaction mixture it reacts with the iodine formed and the solution remains colourless.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

When all of the sodium thiosulphate present has reacted, iodine, I2, will appear in the solution producing an immediate blue colour with starch indicator. In a series of experiments where the concentration of a reagent is changed
Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3
can be used as a measure of rate, √the volume of the reagent used can be taken as a measure of its concentration providing the total volume of the mixture is kept constant in each experiment. The order of reaction with respect to hydrogen peroxide can be obtained by plotting a graph of log rate against log (Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3 )

You are required to investigate the effect of concentration on the rate of reaction,

√20 cm3 of distilled water

Add to the flask from the burette 1.00 cm3 of FB3, sodium thiosulphate.

Add six drops of starch indicator to the mixture in the flask.

Run 20.00 cm3 of FB4, hydrogen peroxide, from the second burette into a 100 cm3 beaker.

Use the measuring cylinder labeled B to add 20 cm3 of FB1, sulphuric acid, to the hydrogen peroxide in the beaker.

Transfer (tip) the contents of the beaker into the conical flask and immediately start a stop-clock or note the start time on a clock with a second hand. Swirl the flask to mix the reagents.

Observe the solution and stop the clock or note the time when the solution suddenly turns blue.

Record the time taken to the nearest second in the table that follows.
Empty, thoroughly rinse and drain the conical flask used in experiment 1.

Repeat the entire procedure for each of the experiments 2 through to 4, each time emptying rinsing and draining the conical flask;

b) Table

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

c) Use your recorded results to plot a graph of (1/time) against (volume of FB4).

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

d) Calculate the gradient of the line drawn, which is the rate of reaction with respect to hydrogen peroxide. ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………

e) The experimental method can be modified to enable the rate of reaction with respect to iodide ions,Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3 , to be investigated. You will perform two further experiments using the method for procedure 1.

You will keep the concentration of hydrogen peroxide constant and reduce the concentration of iodide ions.

f). Procedure II

First copy your reaction time from experiment 1 in section (a) into the table below. Then complete the table below to show the volumes of FB2 and distilled water you will use in these two further experiments.

Carry out each experiment as before and record the time taken in each case.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

(g) Use the experimental results from the three experiments to draw a conclusion as to how the rate of reaction is affected by changing the concentration of iodide ions.
……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………… ………………………………………………………………………………………………………………
h) From your graph find the time taken for the color to change using 12.0 cm3 of FB4 and 28 cm3 of water.

 19 marks

3.

(I) You are provided with solution FA7. Carry out the tests below. Write your observations and inferences in the spaces provided.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

II. You are provided with solution FA8 in a boiling tube. Carry out the tests below. Write your observations and inferences in the spaces provided.

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

Chemistry Paper 3 Question Paper - KCSE CLUSTER TESTS 3

 80 marks

KCSE CLUSTER TESTS 3

Chemistry Paper 3

1.

Question 1

(a) Table.

i) Complete table 1 mark;

Conditions:

– Complete table with 3 titration = l mark;

– Incomplete table with 2 titrations = ‘A mark;

– Incomplete table with 1 titration = 0 mark;

Conditions:

– Accept only 1 to 2dp used consistently; otherwise penalize fully;

– Accept 2dp only if the second d.p is “0” or “5”; otherwise penalize FULLY;

– Accept inconsistency in us of ‘zeros’ as initial volume i. e 0, 0.0, 0.00.

(iii) Accuracy = l mark (only tick the correct value otherwise don’t tick);

– Compare the candidates // students value with the school value (SV); and tick (√) the chosen value where it earns a mark;

Conditions:

– If any vale is within Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 30.10 cm3 of SV = l mark;

– If No value is within Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 30.10 cm3 but at least one is within 0.20 of SV = ½ mark;

– If no value is within 0.20 cm3 of SV = 0 mark

Note: – If there is wrong arithmetic // subtraction in the table compare the SV with the worked out correct value // the titre and award accordingly; (

Penalties: – Wrong arithmetic // subtraction;

– Inverted tables;

– Burette readings beyond 50.0 cm3, unless explained;

– Unrealistic titre values i.e. too low (below 1.0 cm3) or too high (100 cm3);

Note:

– Penalize ½ mark EACH to a maximum penalty of ½ mark (i. e penalize ½ mark only once);

(ii) Use of decimals (tied to rows 1 and 2 only) = l mark

(b) Principles of averaging = l mark;

– Values averaged MUST be shown and MUST be within Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 30.20 cm3 of each other;

Conditions:

– If three consistent values are averaged = l mark;

– If 3 titrations are done but only 2 are within 0.20 cm3 of each other rare averaged = l mark;

– If only 2 titrations are done, are consistent and are averaged = ½ mark;

– If 3 possible but only 2 re averaged = 0 mark;

– If 3 titrations are done, are inconsistent and yet are ALL averaged = 0 mark;

– If only 2 titrations done, are inconsistent and yet averaged = 0 mark; Penalties:

– Penalize ½ mark for wrong arithmetic error outside + 2 units in the second decimal place.

– Penalize ½ mark if no working is shown but the answer is correct;

– If now working is shown and the answer is wrong, penalize fully;

– Accept rounding off the answer to 2 decimal places;

– Otherwise penalize ½ mark for wrong rounding off to l dp or to whole numbers;

c) i) Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

(ii) 250 cm3=0.017 moles

Titre volume in (b) Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

(iii) Using mole ratio, moles in 25cm3 of FA1:

=½ x answer in (c) (ii) above;

=Final answer (x);

25 cm3= Final answer (x);

Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

(iv) Mass =Moles x RMM

of NaCO3=106

Mass per litre = answer in (iii) x 106;

Final answer (q);

(v) Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

 14 marks

2.

Question 2

(b) Table.

(i) Complete table with 8 readings… l mark

Penalties and conditions:

– Penalize ½ mark for each space not filled;

– Reject fractions for height of precipitate and award a maximum of 2½ marks for the table (height row)

– Penalize ½ mark each for entry not in mm in the time column e.g. 2.5 cm.

(ii) …………………………. . Use of decimals. ……..½ mark

– Accept readings in 1 to 2d.p used consistently throughout; otherwise penalize fully (time column).

(iii) Accuracy……………………..l mark

– Compare the candidates Ist time reading with the school value.

– If within ± 2 seconds award l mark; otherwise penalize fully. (iv) Trend…………………………… 1 mark (time row)

-Award l mark if time is decreasing to downwards;

– Where values of time are constant, mark only the first constant value and reject the rest. If two constant values are following each other mark one and reject the other.

(c) Graph;

Trend

Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

Marking:

Final answer;

(i). Scale. ……………………….. ½ mark;

– Area covered by actual plots including the origin should be ¾ of the space provided for the plot.

– The scale should accommodate the 4 plots; otherwise penalize fully.

– The scale must be consistent on both axes otherwise penalize fully;

(ii) Labeling of the axes……………………………………………………. ½ mark;

Conditions:

– Penalize ½ mark for wrong units used.

– Penalize ½ mark for inverted axis;

– Accept if no are shown on labelling; but both axes must be correctly labeled;

(iii). Plotting …………………… .2 marks;

– Accept 3 or 4 plots correctly plotted for 2 marks;

– If 2 points are correctly plotted, award l mark;

– If only 1 point is correctly plotted award 0 mark;

– If the points for the table are to 3 or more dps and rounded off to 2dp on plotting penalize ½ mark once;

otherwise accept rounding off to 3 decimal places;

(iv). Line ………………….. l mark;

– Accept a straight line passing through at least 2 points correctly plotted and through the origin; otherwise penalize fully;

(d). Gradient.

– Construction lines drawn on the graph.

– The hypotenuse of the constructed “triangle” should cover at least half of the length of the line drawn by the candidate.

– Correctly reads (to nearest ½ small square) the coordinates from the graph

– Accept values from the table if the line is drawn through the point.

– Do not penalize reuse of values for an incorrectly plotted point

– Calculates gradient correctly to at least 1 decimal place using the values read from the graph by the candidate.

Maximum score: 3 marks;

(f) Has:

– Variable volume of water,½ mark;

– Water to keep total combined volume (FB 4 and water) constant at 40 cm3; ½ mark;

– Record the volume of (FB 4 + water) for each experiment to the left of the table.

– Complete table; l mark;

– Correct and consistent use of decimals; l mark;

(g). Uses experimental data to make appropriate comment, from experimental results, as to how rate varies with concentration of KI. (Do not give this mark where mixtures selected in (J) are not appropriate, i.e. the volume of (FB 4 + water) -f 40 cm3) where an acceptable qualitative statement has been given ignore any incorrect attempt at a quantitative/mathematical expression Showing on the graph = ½ mark;

Correct value read from graph =½ mark

 19 marks

3.

Chemistry Paper 3 Marking Scheme - KCSE CLUSTER TESTS 3

 80 marks

KCSE 2021-2022 Chemistry Paper Three Leakage Details

POLITE NOTICE! THERE IS NO KCSE LEAKAGE FOR KCSE Chemistry PAPER THREE. KCSE CANDIDATES ARE THEREFORE ADVISED TO THOROUGHLY PREPARE.

 

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