QUESTIONS
You are provided with:
 Solid F
 2.0 M hydrochloric acid solution G
 0.1 M sodium hydroxide
 You are required to determine the;
Enthalpy change ΔH, for the reaction between solid F and one mole of hydrochloric acid
Procedure:
Using a burette place 20.0cm^{3} of 2.0M hydrochloric acid, solution G in a 100ml beaker. Measure the initial temperature of the solution after every ½ minute and record the values in table 1 below. At exactly 2 minutes, add all of solid F to the acid. Stir the mixture gently with the thermometer. Measure the temperature of the mixture after every halfminute and complete the table. (Retain the mixture for use in procedure II)
Table 1
Time(min) 0 ½ 1 1½ 2 2½ 3 3½ 4 4½ 5 Temperature (ºC)  Plot a graph of temperature (yaxis) against time.(3 marks)
 From the graph determine the change in temperature ΔT (1mark)
 Calculate the heat change for the reaction (Assume the specific heat capacity of the mixture is 4.2 J g1 K1 and the density of the mixture is 1g/cm^{3})(1mark)
Procedure II
Rinse the burette thoroughly and fill it with sodium hydroxide. Transfer all the contents of the 100ml beaker from procedure I above into a 250ml volumetric flask, add distilled water to make up to the mark. Label this solution H. using a pipette and a pipette filler, place 25cm^{3} of solution H into a 250ml conical flask. Add two to three drops of phenolphthalein indicator and titrate against sodium hydroxide. Record your results in table 2. Repeat the titration two more times and complete the table.
Table 2I II III Final burette reading (cm^{3}) Initial burette reading (cm^{3}) Volume of solution solution D used (cm^{3})  Average volume of sodium hydroxide used (1mark)
 Number of moles of:
 Sodium hydroxide used (1 mark)
 Hydrochloric acid in 25cm^{3} of solution H (1 mark)
 Hydrochloric acid in 250cm^{3} of solution H (1 mark)
 Hydrochloric acid in 20cm^{3} of solution G (1 mark)
 Hydrochloric acid reacted with solid F (1 mark)
 Calculate the enthalpy of reaction between solid F and one mole of hydrochloric acid. (Show the sign of ΔH) (1 mark)
 You are provided with solid A. Carry out the tests described below and write your observations and inferences accordingly.
 Dissolve solid A in about 10cm^{3 }of distilled water in a boiling tube divide the resulting solution into five portions.
 To the first portion and 5 drops of 2M sodium hydroxide solution
 To the second portion dip a glass rod to one of the remaining portions and heat it in a nonluminous flame.
 To the third portion add 2 or 3 drops of lead (II) nitrate solution
 To the forth portion add 2 or 3 drops of barium (II) chloride followed by 2cm^{3} of 2M hydrochloric acid. Shake the mixture well.
 To the fifth portion add 3 drops of acidified potassium manganate (VII) solution
 You are provided with substance B.
Carry out the tests described below and record your observations and inferences accordingly.
Procedure Place a little amount of substance B in a metallic spatula and ignite it in a blue bunsen burner flame.
 Place a spatulaful of substance B in a boiling tube. Add about 20cm^{3} of distilled water and shake well. Divide the solution into three portions. Test the pH of one portion of the solution above using a full range pH chart.
 Add the sodium carbonate provided to the second portion.
 Add a few drops of potassium manganate (VII) solution to the third portion and warm mixture.
CONFIDENTIAL
In addition to the apparatus and fittings found in the chemistry laboratory, each candidate will require the following:
 2.1g of solid F (NaHCO_{3}) weighed accurately and supplied in a dry stoppered container.
 About 60cm^{3} of solution G(2M HCl)
 About 130cm^{3} of solution of sodium hydroxide solution.(0.1M )
 One thermometer 10ºC – 110ºC
 One stop watch/ clock
 One 100ml plastic beaker
 One burette 0 – 50ml
 One pipette 25ml
 One 250ml volumetric flask
 About 500cm^{3} of distilled water supplied in a wash bottle
 One label or means of labelling
 One pipette filler
 Two conical flasks
 Clamp and stand
 About 0.2g of solid A (Na2SO_{3})supplied in a stoppered container
 0.2g of solid B (maleic acid)
 Six clean dry testtubes and One boiling tube
 One metallic spatula
 Glass rod
 About 0.2g of sodium carbonate(solid)
 2cm piece of pH paper
ACCESS TO
 Means of heating.
 2M aqueous sodium hydroxide supplied with a dropper
 Acidified potassium manganate (VII) supplied with a dropper
 Phenolphthalein indicator supplied with a dropper
 Full range pH chart
 Lead (II) nitrate supplied with a dropper(0.5M)
 Barium (II) chloride supplied with a dropper(0.5M)
 2M hydrochloric acid supplied with a dropper
NOTES
 Solution G is prepared by adding 172.0cm^{3} (1.28g/cm3) of concentrated hydrochloric acid to about 500cm^{3} of distilled water and diluting to one litre of solution. (2M HCI)
 Acidified potassium manganate (VII) is made by dissolving 3.16g of the solid in about 500cm3 of 2M H_{2}SO_{4} and diluting to one litre of solution. (0.02M KMnO_{4})
 Sodium hydroxide is prepared by dissolving 4g of the solid in about 700cm^{3} of water then diluting to one litre.(0.1M NaOH)
MARKING SCHEME
Table 1
 Complete table ……………… 2 mks
Penalties / conditions
Penalize ½ mk for each space not filled in the temperature row upto a maximum  Use of decimals – 1mk
Accept whole numbers or decimals up to 1 dec place (either .0 or .5) or 2nddec. (, 25, .50 or .75) used consistently, otherwise penalize fully.  Accuracy  1 mk
Compare the candidate’s first temperature reading to the school value (teacher’s first temperature reading)
If within ± 2.0ºC, award 1mk, otherwise penalize fully.  Trend 1mk
Award 1mk if temperature remains constant from 0 min to 1½ min , then a drop followed by a continous rise otherwise penalise fully
 GRAPH.
Labeling of axes (both)  ½ mk) Penalise ½ mk for wrong units used in any of the axis otherwise ignore if units not given.
 Penalise ½ mk for inverted axis
 Accept for ½ mk if no units shown on labeling.
Scale ½mk  Area covered by actual plots must be at least half of the big squares ( y – axis) and half of the big squares ( x – axis)otherwise give zero.
 Scale used must be consistent on both axes, otherwise penalise fully.
Plotting 1mk  Accept 8 or 9 points correctly plotted for 1mk
 If 5 or 7 points are correctly plotted award ½ mk
 If less than 5 points are correctly plotted gives Zero
 Accept correct plots even if the axes are interchanged.
The lines1mk  Accept for ½ mark an extrapolated straight line passing through at least 2 correctly plotted points from time 0 min to 1½ min. Award another ½ mark for another extrapolated straight line passing through at least 2 correctly plotted points from time 2½ min to 5 min
 Showing on the graph √ ½ mk (extrapolation at time 2 minutes)
 Stating the correct reading of ΔT√ ½ mk
Conditions  penalise√ ½ mk if not shown on the graph to obtain the value.
 Award 1mk if not shown on graph and not recorded but used correctly in the expression.(mcΔT)
 Award 0 mk if not shown on the graph and value stated is wrong.
 Stating the correct reading of ΔT√ ½ mk
 Heat change for the reactio
ΔH = mc ΔT
= 20×4.2×ΔT
1000 √
=correct answer kJ √½
Penalties / conditions
 Accept answer given in joules /kilo joules ignore sign if given however penalize ½ for –ve
 Otherwise penalize ½ mk for wrong units given
PROCEDURE II
TABLE 2 ……………..Total 5 mks distributed as below
 Complete table 1mk
Complete table with 3 titrations 1mk
Penalties Unrealistic titre values i.e. values below 1cm3 or hundreds
 Burette readings beyond 50cm^{3} unless explained
 Inverted table
 Wrong arithmetic
N/B: Penalize ½ mk each for a maximum of ½ mk
 Decimals 1mk(Tied to the 1st and 2nd rows only)
Should be 1 decimal place or 2 decimal places used consistently otherwise penalise fully.
The 2nd decimal place should either be a 0 or 5  Accuracy 1mk
 If any titre value within ± 0.1 of the school value award 1mk
 If any titre within ± 0.2 of the school value ½ mk
 If none of the titre values is within ± 0.2 of school value (s.v)award 0mk
 Principles of Averaging 1mk
Values to be averaged MUST be shown and MUST be within ± 0.2 of each other
Conditions If 3 consistent values are averaged 1mk
 3 titrations done only 2 are possible and averaged 1mk
 3 consistent values but only 2 are averaged award 0mk
 3 inconsistent values are average award 0mk
Penalties Penalise ½ mk for arithmetic error in answer outside ± 2 units in the 2nddec. Place.
 Penalise ½ mk for NO WORKING shown but the answer is correct.
 Accept rounding off to the 2nddec.places otherwise penalise ½ mk if answer is rounded off to 1stdec. place unless values divide exactly to 1 dec. place
 Final answer 1mk
(Compared to school value (S.V) Tied to correct average titre) If within ± 0.1 of S.V  award 1mk
 If within ± 0.2 of S.V  award ½mk
 If beyond ± 0.2 of S.V award 0mk
 Average titre x 1.5 mk =Correct answer
1000
Condition /penalties Penalise ½ mk for wrong Transfer (WT) of titre otherwise Penalise fully for strange value
 1.5 Must be transferred INTACT otherwise penalise fully
 Penalises ½ mk for arithmetic error outside 2 units in the 4thdec. place
 Accept rounding off of the answer to the 4thdec.place
 Units may not be shown but it shown must be correct, otherwise penalise ½ mk for wrong units.

 Moles of sodium hydroxide
= 0.1×average volume
1000
= correct answer  Moles of NaOH: HCI = 1:1 mk
Moles of HCI in 25cm^{3} = correct answer (i) above.√½  Moles of HCI in 250cm^{3}= answer(ii)×250
25
= correct answer √½  Moles of HCI in 20cm^{3} of solution G.
= 2 × 20
1000√½
= correct answer √½  Moles of hydrochloric acid that reacted with solid F
= Answer (iv)  Answer (iii) √½
= correct answer √½
 Moles of sodium hydroxide
 Molar enthalpy of reaction between solid F and one mole of hydrochloric acid
= 1 × answer (c)
answer (v)
= correct answer (+ve) kJ/mol
(penalise ½ mk for ΔH not shown / wrong i.e given as –ve)
Conditions /penalties Penalise ½ mk for wrong Transfer (WT) of Answer (ii), otherswisepenalise fully for strange value
 Penalise ½ mk for an arithmetic error outside ± 2 units in the 4thdec. place
 Same as (iv) in II above
 Same as (v) in II above
 Moles in 100cm^{3} of solution T
Answer 111 x 100 = Correct Answer
25
Conditions/ penalties penalise ½ mk for arithmetic error outside 2 units in the 4thdec. place
 Penalise ½ mk for wrong transfer / rounding off of answer 111
 Same as (IV) in 11 above
 Same as (V) in 11 above
Moles ratio for reaching of Mg to H_{2}SO_{4} is 1:1
Moles of H_{2}SO_{4} used in procedure 1
Answer 1 (d)
Answer 1 (d) + Answer iv = Correct Answer
Conditions / penalties Penalise ½ mk for WT of Answer 1 (d) or answer (iv) or for both otherwise penalise fully for strange value.
 Penalise ½ mark for arithmetic error outside ± 2 units in the 4thdec. place.
 Molarity of solution Q  H_{2}SO_{4}1000×answer (iv) = Correct answer
50
Conditions /penalties
Penalise ½ mk for wrong Transfer of answer (ii) to (iv) otherwise penalize fully for strange value.
Question 2
Observations  Inferences 


Question 3
Observations  Inferences 


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