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CONFIDENTIAL    

INSTRUCTIONS

Each candidate should have :

 

  • 80 cm3 of solution T
  • 100 cm3 of solution S
  • Exactly 1.5g of solid V
  • 250cm3 beaker (glass)
  • 1 label
  • 1 pipette
  • 1 burette
  • 100cm3 measuring cylinder
  • 1.2g
  • 120cm3 plastic beaker
  • A stop clock /watch
  • About 1.0g of solid J
  • 1 boiling tube
  • 1 metallic spatula
  • 1 glass rod
  • 5 test tubes
  • 1 filter paper

 

Access to:

  • Phenolphthalein
  • 2m lead (II) nitrate
  • 0.05 M sodium thiosulphate
  • Distilled water
  • 20% volume hydrogen peroxide
  • Source of heat ( Bunsen burner)

 

Notes:

  • 20% 20 volume peroxide is prepared by diluting 20cm3 of 20v hydrogen peroxide

to make 100cm3

  • solution T is 1.0 hydrochloric acid and is made by dissolution 86cm3 of 35-37% hydrochloric acid diluted to 1litre of solution
  • solution S is 0.5m sodium hydroxide
  • solid V is exactly 1.5g of sodium carbonate ( anhydrous)  
  • solid J is potassium iodide
  • solid M is 1.2g magnesium powder
  • solution K is 0.02m copper (II) sulphate

 

1.  You are provided with the following :  

  • 1.0M Hydrochloric acid; solution T.  
  • 0.5M sodium hydroxide; solution S  
  • Anhydrous sodium carbonate of unknown mass: solid V.  

You are required to determine the mass of sodium. Carbonate that was used in the experiment.

 

Procedure

Measure 60cm3 portion of 1m hydrochloric acid using a measuring cylinder and transfer

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it to 100cm3 beaker. Add all sodium carbonate (solid V) to the acid in the beaker and

stir gently. Leave the mixture for 3 minutes until there is no effervescence transfer

the mixture into a clean 100ml measuring cylinder and add distilled water to make

100cm3 of the solution. Transfer all the solution into 250cm3 beaker and shake

well, label this solution W.

Fill the burette with solution S.

Pipette 25.0cm3 of solution W and transfer to a conical flask. Add 2-3 drops of phenolphthalein indicator and titrate with solution S. Records your results in table I below.

Repeat the titration to get two more concordant values.

 

 Table I

Experiment

I

II

III

Final burette reading (cm3)

   

initial burette reading (cm3)

   

Volume of solutions S used

   

 

  Transfer the mixture into a clean 100ml- measuring cylinder and add distilled water to

make 100cm3 of the solution.

 (a) Determine the average volume of solution S used.    

 (b). Calculate the number of moles of sodium hydroxide (solution S) used.  

(c). Find the number of moles of hydrochloric acid in 25cm3 of solution W.    

 (d). Determine the number of moles of hydrochloric acid in 100cm3

 (e). Calculate the number of moles of hydrochloric acid in the original 60cm3 of solution.

 (f). Calculate the number of moles of hydrochloric acid that reacted with sodium

carbonate.

(g). Determine the mass of sodium carbonate that reacted with the acid. (Na= 23, C= 12, 0= 16).

 

2.  You are provided with the following.    

 (i). 1.2g Magnesium powder, solid M

 (ii). 0.02M copper (ii) sulphate, solution K  

You are required to determine the molar enthalpy of displacement for the reaction

between

magnesium powder and copper (II) sulphate solution.  

Procedure

Measure out 100cm3 of solution K into a plastic beaker.

Measure the temperature of this solution at every minute for four minutes. Add the entire amount of solid M to the contents of the plastic beaker at the fourth minute. Stir with the thermometer. Record the temperature after every half-a- minute in table II below.

 

Table II

 

Time (min)

0

½

1

1 ½

2

21/6

3

3 ½

4

4 ½

5

6

Temp.(oC)

              

 

(a). Draw the graph of temperature (oC) against time, t (in minutes) ) Use your graph to

get the temperature rise.

 (b). Calculate the heat lost by the solution

 (Specific heat capacity of solution = 4..2Jg -1K-I, density of solution = 1g/cm3)  

(c). Write an ionic equation for the reaction.    

(d). Calculate the number of moles of :

  (i). Copper (ii) ions in the original solution.  

  (ii). Magnesium added to the copper (ii) sulphate solution

  (iii). Copper (II) ions displaced by magnesium powder.

  (Mg = 24, Cu = 63.5, S = 32, O = 16)

(e). Calculate the molar heat of displacement of copper (II) ions by magnesium powder.  

(f). Comment on the value of the molar heat if ion powder had been used instead magnesium

powder . Explain.

(a). (i)You are provided with solid J.

(ii). To the filtrate above, dip a clean metallic spatula and burn a drop of the filtrate

on it with a non-luminous flame.

  (iii). Divide the filtrate into two equal populations.

I. To the 1st portion add 2m lead (ii) nitrate.

II. To the second portion add 3 -5 drops of 20% 20 – Volume hydrogen peroxide

(iv). To the resulting mixture in (ii) above, add about 1cm3 of sodium thiosulphate

solution Q. From the tests carried out above identify.

(i). Cation

(ii). Anion


 




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