Chemistry Paper 3 Questions and Confidential - ACK Diocese Mumias Joint Evaluation Mock 2022

Questions

INSTRUCTIONS TO CANDIDATES

• Answer all the questions in the spaces provided in this question paper.
• You are NOT allowed to start working with the apparatus for the first 15 minutes of the 2 ¼ hours allowed for 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 MUST be clearly shown where necessary
• Mathematical tables and electronic calculators may be used.
•  Candidates should answer questions in English.

1. You are provided with:
   • 0.1M Sodium hydroxide, Solution F
   • Solution G made by dissolving 12.6g of dibasic acid, H2J2O4 ,in 250cm3 of distilled water.
   • 0.02M acidified potassium manganate (vii), Solution N.
     
     You are required to:
     1. Dilute Solution G
     2. Standardize the resulting dilute solution using sodium hydroxide Solution F
     3. Determine the mass of J in the formula H₂J₂O₄
     4. Determine the rate of reaction between solution G and solution N at various temperatures.
   • Procedure I
     1. Using a measuring cylinder measure 20cm³ of solution G and transfer into a beaker.
     2. Measure 80cm3of distilled water and add it to the 20cm³ of solution G in the beaker.
     3. Label this solution H.
     4. Place solution H in a burette.
     5. Pipette 25cm3of solution F into a 250cm³ conical flask.
     6. Add 2 drops of phenolphthalein indicator and titrate with solution Record your results in table
     7. Repeat the titrations two more times and complete table 1.
        
        
        1. Table 1 ( 4 marks)
           

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

        2. Calculate the average volume of solution H used ( 1 mark)
        3. Determine the number of moles of:
           1. Sodium hydroxide, Solution F used. (1 mark)
           2. The acid, solution H used ( 2 marks)
           3. Acid in 100cm³ of solution H ( 1 mark)
           4. Acid in 20cm³ of solution G ( 1 mark)
           5. Acid in 250cm³ of solution G (1 mark)
        4. Calculate the:
           1. Molar mass of acid H2J2O4 ( 2 marks)
           2. Mass of J in the formula given H2J2O4 that H=1 and O=16 (1 mark)
              
              
   • Procedure II
     1. Place 5cm3of solution N in a boiling tube.
     2. Place another 5cm3of solution G in a boiling tube
     3. Heat solution N on a Bunsen burner flame to 800C.Allow it to cool to 70°C.Note that care should be taken to prevent breaking of the thermometer.
     4. Add all solution G into solution N and immediately start a stopwatch.
     5. Stir the mixture using a thermometer and record the time taken for the purple colour to disappear.
     6. Clean the boiling tubes and repeat the procedure by allowing solution N to cool to 60°C,50°C,40°C and complete Table 2 below.
        1. Table II (5 marks)
           

           Temperature,°C	70	60	50	40
           Time taken for purple colour to disappear (s)
           Reciprocal of time, 1/time(s-1)

        2. On the grid provided plot a graph of 1/time (y-axis) against temperature. (3 marks)
        3. From the graph determine the time taken for the purple colour to disappear at 450C. ( 1 mark)
        4. State the relationship between the rate of reaction and temperature at which purple colour disappears. ( 1 mark)
2. You are provided with solid P. Put all solid P in a clean boiling tube and add about 10cm3of distilled water and stir. Divide mixture into four portions.
   

   Observation	Inference
   (1 mark)	(1 mark)

   
   
   1. To the first portion, add sodium hydroxide dropwise until in excess.
      

      Observation	Inference
      (1 mark)	(1 mark)

   2. To the second portion, dip a glass rod and burn in a non-luminous flame
      

      Observation	Inference
      (½ mark)	(1 mark)

   3. To the third portion, add 2 drops of Barium nitrate
      

      Observation	Inference
      (½ mark)	(1 mark)

   4. To the fourth portion add 2 drops of acidified potassium manganate (vii)
      [Solution N] using the dropper provided.
      

      Observation	Inference
      (1 mark)	(1 mark)

3. You are provided with Solid R. Carry out the following tests and record your observations and inferences in the tables below.
   1. Using a clean metallic spatula, burn about one third of solid R in a non-luminous flame
      

      Observation	Inference
      (1 mark)	(1 mark)

   2. Dissolve the remaining solid R in about 10cm3distilled water in a test tube and divide the solution into 3 portions.
      To the first portion add 2 drops of potassium manganate (vii) [Solution N] using the dropper provided.
      

      Observation	Inference
      (1 mark)	(1 mark)

   3. To the second portion add two drops of bromine water.
      

      Observation	Inference
      ( ½mark)	(1 mark)

   4. To the third portion add sodium carbonate provided.
      

      Observation	Inference
      (½ mark)	(1 mark)

Confidential

In addition to the common laboratory apparatus and fittings, each candidate shall be supplied with the following:

• 80cm³ of solution F
• 80cm³ of solution G
• 30cm³ of solution N
• One 50cm³ burette
• One 25cm³ pipette
• Two 250cm³ conical flasks
• One 100cm³ measuring cylinder
• One 250cm³ empty beaker
• Distilled water in a wash bottle
• One thermometer
• Source of heat
• Six dry test tubes
• One glass rod
• Two boiling tubes
• One stopwatch
• One clean dropper
• One clean metallic spatula
• One test tube holder
• 0.5g of sodium carbonate
• 0.5g solid P
• 0.5g solid R
  The students should have access to the following:
• Phenolphthalein indicator supplied with a dropper
• Bromine water supplied with a dropper
• 2M sodium hydroxide supplied with a dropper
• 1M barium nitrate supplied with a dropper
  NOTES
  
  1. Bromine water is prepared by adding 1cm³ of liquid bromine to 100cm³ of distilled water and shaking thoroughly.
  2. Solution N is prepared by adding 3.16g of potassium manganate (vii) in 200cm³ of 2M sulphuric (vi) acid and adding water to make one litre.
  3. Solution F is prepared by dissolving 4g of sodium hydroxide in about 800cm³ of distilled water and making up to one litre solution.
  4. Solution G is prepared by dissolving 12.6g of oxalic acid in 400cm³ of distilled water and making the solution up to one litre.
  5. Solid P is sodium sulphite and solid R is oxalic acid.