Bunyore Maranda MOCKS 2016 Chemistry Paper 3

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You are provided with:-
4.5g of solid A in a boiling tube.
Solution B, 0.06 acidified Potassium manganate (VII)

You are require to determine
(1) The solubility of sold A at different temperatures
(2) The number of moles of water of crystallization in solid A.

Procedure
1. Using a burette, add 4cm³ of distilled water to solid A in the boiling tube. Heat the mixture while stirring with the thermometer to about 70^oC. When the entire solid has dissolved, allow the solution to cool while stirring with the thermometer. Note the temperature at which crystals of solid A first appear. Record this temperature in table 1.
2. Using the burette, add 2cm³ of distilled water to the contents of the boiling tube. Warm the mixture while stirring with the thermometer until all the solid dissolves. Allow the mixture to cool while stirring. Note and record the temperature at which crystals of solid A first appear.
3. Repeat procedure(b) two more times and record the temperatures in table I. Retain the contents of the boiling tube for use in procedure (e)
4. 1. Complete table 1 by calculating the solubility of solid A at the different temperatures. The solubility of a substance is the mass of the substance that dissolves in 100cm³ (100g) of water at a particular temperature. (6 marks)
    
    Volume of water in the
    boiling tube (cm³) Temperature at which
    crystals of solid A first
    appear (^oC) Solubility of solid A(g/100g water)
    
    4
    
    6
    
    8
    
    10
  2. On the grid provided, plot a graph of the solubility of solid A (vertical axis against temperature) (3 marks)
  3. Using your graph, determine the temperature at which 100g of solid A would dissolve in 100cm³ of water. (1 mark)
5. 1. Transfer the contents of the boiling tube into a 250ml volumetric flask. Rinse both the boiling tube and the thermometer with distilled water and add to the volumetric flask. Add more distilled water to make up to the mark. Label this solution A. Fill a burette with solution B. Using a pipette and a pipette filler, place 25.0cm³of solution A into conical flasks. Warm the mixture to about 70oC. Titrate the hot solution A with solution B until a permanent pink colour persists. Record your readings in table 2. Repeat the titration two more times and complete table 2. (Retain the remaining solution B for use in question 3)
    
    Table 2
    
    I II III
    
    Final burette reading
    
    Initial burette reading
    
    Volume of solution B used (cm³)
  2. Calculate the:
    1. Average volume of solution B used. (1 mark)
    2. Number of moles of potassium manganate (VII) used. (1 mark)
    3. Number of moles of A 25cm³ of solution A given that 2 moles of potassium manganate (VII) react completely with 5 moles of A. (1 mark)
    4. Relative formula mass of A. (2 marks)
  3. The formula of A has the form D.xH₂O. Determine the value of x in the formula given that the relative formula mass of D is 90.0 and atomic masses of oxygen and hydrogen are 16.0 and 1.0 respectively.
You are provided with 10cm³ P. Solution P contains two cations and one anion. Carry out the tests below and record your observations and inferences in the spaces provided.
1. Add 20cm³ of 2M aqueous sodium hydroxide to all of solution P provided. Shake well. Filter the mixture into conical flask. Retain both and the residue.
  
  Observations Inferences
  
  (1 mark) (1 mark)
2. 1. To about 2cm3 of the filtrate, add 2M nitric acid dropwise until in excess. (i.e about 1 cm3 of the acid). Retain the mixture.
    
    Observations
    
    (1 mark)
    
    Divide the mixture in b(i) above into two portions.
  2. To the first portion, add aqueous sodium hydroxide dropwise until in excess.
    
    Observations Inferences
    
    (1 mark) (2 mark)
  3. To the second portion, add aqueous ammonia dropwise until in excess.
    
    Observations Inferences
    
    (1 mark) (1 mark)
3. To 2cm³ of the filtrate, add 3 drops of potassium iodide solution.
  
  Observations Inferences
  
  (1 mark) (1 mark)
4. To 2cm³ of filtrate, add 3 drops of acidified barium nitrate solution.
  
  Observations Inferences
  
  (1 mark) (1 mark)
5. To the residue in (a) add 8cm³ of dilute nitric acid and allow it to filter into a boiling tube.
  1. To 2cm³ of this filtrate, add aqueous ammonia dropwise until in excess.
    
    Observations Inferences
    
    (1 mark) (1 mark)
Dissolve all of solid G in about 10cm3 of distilled water in a boiling tube. Use the solution for tests (a) to (c) below.
1. Place 2cm³ of the solution in a test tube and add 2 drops of acidified potassium manganate (VII), solution B from the burette.
  
  Observations Inferences
  
  (1 mark) (1 mark)
2. To 2cm³ of the solution in another test-tube, add 2-3 drops of bromine water.
  
  Observations Inferences
  
  (1 mark) (1 mark)
3. To 2cm³ of the solution in a third test-tube add a spatula full of the sodium hydrogen powder provided.
  
  Observations Inferences
  
  (1 mark) (1 mark)

Bunyore Maranda MOCKS 2016 Chemistry Paper 3

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Volume of water in the boiling tube (cm³)	Temperature at which crystals of solid A first appear (^oC)	Solubility of solid A(g/100g water)
4
6
8
10

	I	II	III
Final burette reading
Initial burette reading
Volume of solution B used (cm³)

Observations	Inferences
(1 mark)	(1 mark)

Observations	Inferences
(1 mark)	(2 mark)

Observations	Inferences
(1 mark)	(1 mark)

Observations	Inferences
(1 mark)	(1 mark)