23.6.3 Chemistry Paper 3(233/3) N am e... Index No... /, 233/3 CHEMISTRY Paper 3 PRACTICAL Oct./Nov. 2007 2 ^ hours Candidate s Signature D a te... THE KENYA NATIONAL EXAMINATIONS COUNCIL Kenya Certificate o f Secondary Education CHEMISTRY Paper 3 PRACTICAL 2 hours Write your name and index number in the spaces provided above, Sign and write the date o f examination in the spaces provided above Answer ALL the questions in the spaces provided in the question paper. You are NOT allowed to start working with the apparatus for the first 15 minutes o f the 2 j hours allowed fo r this paper. This time is to enable you to read the question paper and make sure you have all the chemicals and apparatus that you may need. All working M UST be clearly shown where necessary. Mathematical tables and electronic calculators may be used. For Examiner s use only Question 1 Maximum Score 22 2 11 3 07 C andidate s Score Total Score 40 This paper consists of 8 printed pages Candidates should check the question paper to ascertain that all the pages are printed as indicated and no questions are missing. 702S O 2007 The Kenya National Examinations Council T «m over 298
I You are provided with:» aqueous sulphuric acid labelled solution A * solution 8 containing 8.0 g per litre of sodium carbonate an aqueous solution of substance C labelled solution C, You are required to determine the: * concentration of solution A * enthaiphy of reaction between sulphuric acid a»d substance. A Procedure Using a pipette and a pipette filler, place 25.0 cm3of solution A into a 250 ml. volumetric flask. Add distilled water to make 250 cm3 of solution. Label this solution D. Place solution Dina burette. Clean the pipette and use it to place 25.0 cm' of solution B into a conical flask. Add 2 drops of methyl orange indicator provided and titrate with solution D. Record your results in table!. Repeat the titration two more times and complete the table. Table 1 Final burette reading Initial burette reading I 11 m Volume of solution D used (cm3) (3 marks) Calculate the: (i) average volume of solution D used (I mark) (ii) concentration of sodium carbonate in solution B (Na = 23.0; O = 16.0; C = 12.0) (1 mark) (iii) concentration o f sulphuric acid in solution D (2 marks) (iv) concentration of sulphuric acid in solution A. (t mark) 299
B Label six test-tubes as 1,2,3,4,5 and 6. Empty the burette and fill it with solution A. From the burette, place 2 cm3of solution A into test-tube number i. From the same burette, place 4 cmj of solution A in test-tube number 2. Repeat the process for test-tube numbers 3,4,5 and 6 as shown in table 2. Clean the burette and fill it with solution C, From the burette, piace 14 cm3 of solution C into a boiling tube, Measure the initial temperature of solution C to the nearest 0,5 C and record it in table 2, Add the contents of test-tube number 1 to the boiling tube containing solution C. Stir the mixture with the thermometer. Note and record the highest temperature reached in table 2. Repeat the process with the other volumes of solution C given in table 2 and complete the table. Table 2 Test-tube number 1 2 3 4 S 6 Volume of solution A (cm3) 2 4 6 8 10 12 Volume of solution C (cm3) 14 12 10 8 6 4 Initial temperature of solution C ( C) Highest temperature of mixture ( C) Change in temperature, AT ( C) (6 marks) 300
(i) On the grid provided, draw a graph of AT (vertical axis) against volume of solution A used. (3 marks) 7 T T X i T T Z p i r 1 : n T T T T F T ' T : T ^ r r ^ ; : I : i I T T T a '' 4444'l4-S--4--f- *--4-1t - - ---pt - ^ c i t *- *] ( ( ^*, 44.4^444-^x! 4444Xi-i.-i...,... 4 j. - *. i * < it- 4 - t i x t t l i t t i t ' t i t f i i x,.ry..*,.,4....f - «r * t * ' * * *» >1 * *. 1, s 7 7 i. 1 11, Z,, - i *. ;, *!,T - *' *!* 'i t! * 1 i 4 - * * -_ * - - ^, 1 ' i.i.x ^»* H S E F F E h ^v x x x i x - x f T :, T X ; - ;. *..1 * t, +*» * j j., } }, * I* 1 f r r 1 *. i - 1 _ 4 * 1 I,. *. X j JX X * I, *' *j * ** -{I* S * * - i X * * ^* t - * w r, -»** * - ^*» ~ - 1 i*-. *, i * < r * * * f **t - *» j * j. f-ff i i i-f4'4- ^ 4 4 X 4 4.++: ^ ' * 1 - X I J. 1 -, «* -t * f r * * <. ) 7T- * 7 ^ ' T t t f - 7 7 * ' r " f!. r r...*.... ' ~ i -I.-* ~ X -' {* 1 - - *. 1 7 f 4 i 1 l i i j d x l i ". ' t o i j i i l i : ''{' 44rfTT''r 4*1. >1-1 4^ 4*4444«4... *i - ; a \, r - - f - k * *. t -- - * *- 4»l ^ t t - M 4-4--f j'-yi't t-f-- - t <i t \ 1 ] }. M Tt j j * I ; ] j 7 *t, -, ' -r{-4-:j-"r -'f'f...j..-j..j. ---- f e t t r n a T fi-f >? j ^ * V : f f ± : d ± ; : * j 1 4 1..i'4 'n x c i.x ; x p n x f Ct-C A* ; U!!- t \ 1 ** 1 -, - f, *, 4 i, * * > M i -Cl,, - ^ i i x * * * ' * - *-«* u - i J-* T *.IX lx l- X x tx. \ t * [ ^, t f i T i r n r i r i r i x c i T " ~4 i I '* 1,, t *..l4 Xi: :i::!4 :..1 4. i : ; s 1 s ( ~S 1 v *,. *. } «* * J MiUif' * T * t t 1 *. ' 4 ; : : 4 ; 1 * * r " j t n t r r "^Xi'T- 1 1 * f * ) t, * 1 ' M ' * 1 v " 1 r v! } 1 t i i n. ], r! : r t......... -f'f 4 i,,t',h-4 * I i k I x! t - t f t f f p f e i t X ; 4.. r ] i. 7 + t r - r,, t n i 1 i ^*: 4 t l f~ r- f* 1 >***, Y f ^,,» V J-.. L 1, * «L r * * *? * n 1 (ii) (iii) From the graph, determine; I the maximum change in temperature (I mark) II the volume of solution A required to give the maximum change in temperature. (I mark) Calculate the: I number of moles of sulphuric acid required to give the maximum change in temperature (I mark) 301
H mofar enthalpy of reaction between sufphuric acid and substance G (in kifojoules per mote of sulphuric acid). Assume the specific heat capacity of the solution is 4.2Jg lk '' and density of -3 solution is 1.0 gem (2 marks) 2 You are provided with solid E. Carry out the tests below. Write your observations and inferences in the spaces provided. (a) Place one half of solid E in a clean dry test-tube and heat it strongly. Test any gases produced with blue and red litmus papers. (b) Observations x <2 m arks) Inferences (1 mark) Place the other half o f solid E in a boiling tube. Add about 10 cm3 of distilled water and shake until all the solid dissolves. (Use the solution for tests (i), (ii), (iii) and (iv>.) (i) Place two or three drops of the solution in a test-tube. Add 3 cm3 of distilled water. Add two drops of universal indicator to the mixture obtained and then determine the PH of the mixture. O bservations Inferences (1 mark) (1 m a r k ) (ii) 3 To about 1 cm of the solution in a test-tube, add aqueous ammonia drop-wise until in excess. O bservations Inferences (1 mark) ( I m a r k ) (iii) To 2 em ' o f the solution in a test-tube, add three or four drops o f solution G (aqueous potassium iodide.) O b serv atio n s In ferences (1 mark) (1 m a r k ) (iv) To about I cm3 of the solution in a test-tube, add four or five drops of barium nitrate solution. Shake the mixture then add about I cm3 of dilute nitric acid and allow the mixture to stand for about 2 minutes. O bservations J Inferences (i mark) (1 m a r k ) 302
3 You are provided with liquid F. Carry out the tests below. Record your observations and inferences in the spaces provided. (a) Place three or four drops of liquid F on a watch glass. Ignite the liquid using a Bunsen burner. O bservations j Inferences (1 mark) (1 m ark) 3 3 ' (b) To about 1cm of liquid F in a test-tube, add about 1 cm of distilled water and shake thoroughly. Observations j Inferences ( jr mark) (jr mark) (c) To about 1 cm3 of liquid F in a test-tube, add a small amount of solid sodium carbonate. Observations j Inferences (1 mark) (1 m ark) (d) To about 2 cm3 of liquid F in a test-tube, add about I cm3 of solution H [acidified potassium dichromate(vi). Warm the mixture gently and allow it to stand for'about one minute. Observations j Inferences (1 mark) (1 m ark) 303