Chemistry Paper 3 Questions and Answers with Confidential - Kassu Jet Joint Mock Exams 2023

INSTRUCTIONS

• All working MUST be clearly shown.

1.  
   1. You are provided with the following solutions:
      • Solution P, 1M hydrochloric acid
      • Solution Q, 1M sodium hydroxide
        You are required to determine the molar heat of neutralization of hydrochloric acid.
        Procedure
        Measure 23cm³ of P and put in a 100ml beaker. Measure its temperature and record in the table I in the first column. Using a measuring cylinder, measure 5cm³ of Q and add to P in the beaker. Stir with the thermometer and record the final steady temperature. Continue adding 5cm³ of Q at a time and recording the temperature until 35cm³ of P has been added and complete the table.
        Table I
        

        Volume of Q added (cm3)	0	5	10	15	20	25	30	35
        Temperature (°c)

        
        (4marks)
        1. Plot a graph of temperature (vertical axis) against volume of sodium hydroxide, solution Q added. (3 marks)
           
        2. From your graph determine:
           1. Volume of 1M NaOH needed to neutralize 23cm³ of 1M HCl (1mark)
           2. Rise in temperature ΔT. (1mark)
        3. Calculate the amount of heat evolved in the above reaction. (Take specific heat capacity of solution to be 4.2J/g/°C, density of solution 1glcm³) (2 marks)
        4. Calculate the number of moles of HCl used. (1mark)
        5. Hence, determine the molar heat of neutralization of hydrochloric acid. (2 marks)
   2. You are provided with:
      • Solution A, sodium hydroxide
      • Solution C, 0.1M hydrochloric acid
        You are required to:
      • Dilute solution A with distilled water
      • Standardize the diluted solution A with solution C.
        Procedure:
        Fill the burette with solution C.
        Pipette 25cm³ of solution A into a 250cm³ conical flask. Measure 175cm³ of distilled water using a 100cm³ measuring cylinder and add it to solution A in the conical flask. Shake well. Label this as solution D. Pipette 25cm³ of solution D into a 250cm³ conical flask. Titrate with solution C using two drops of phenolphthalein indicator. Record your results in table II below. Repeat this procedure to obtain consistent values.
        Table II
        

        	1st	2nd	3rd
        Final burette reading (cm3)
        Initial burette reading (cm3)
        Volume of solution c used (cm3)

        (4 marks)
        1. Calculate the average volume of solution C used. (1mark)
        2. Calculate the concentration, in moles per liter, of the sodium hydroxide in solution D (2mark)
        3. Calculate the concentration, in moles per litre, of the sodium hydroxide solution A (1mark)
2. You are provided with solid E. Carry out the tests below and, record your observations and inferences in the spaces provided
   1. Place half of solid E in a boiling tube add 10cm³ of distilled water and shake
      

      obsevations	interferences
      (1mark)	(1mark)

   2.  
      1. To about 1cm³ of solution Add 2M NaOH dropwise in excess
         

         observaions	interferences
         (1mark)	(1mark)

      2. To about 1cm³ of solution in a test tube and add 2-3 drops of acidified Barium nitrate
         

         observations	interferences
         (1mark)	(1mark)

      3. To about 1cm³ of solution, add 4-5 drops of acidified potassium manganate (VII) solution
         

         observation	interferences
         (1mark)	(1mark)

      4. Dip a clean glass rod in the remaining portion of the solution and ignite on a nonluminous flame.
         

         observation	interferences
         (1mark)	(1mark)

3. You are provided with solid K. Carry out the tests below and write your observation and inferences in the spaces provided.
   1. Place a spatula full of solid K on a clean metallic spatula and ignite it in a non- luminous flame.
      

      observation	interferences
      (1⁄2mark)	(1⁄2mark)

   2. Place the remaining solid K in a clean boing tube. Add about 6cm³ of distilled water and shake. Divide the resulting solution into three portions.
      

      observation	interferences
      (1mark)	(1mark)

      
      
      1. To the first portion and 2 drops of acidified potassium manganate (VII).
         

         observation	inerferences
         (1mark)	(1mark)

      2. To the second portion, add all of the solid sodium carbonate provided.
         

         observation	interferences
         (1mark)	(1mark)

      3. Using the third portion, determine the pH.
         

         observation	interferences
         (1⁄2mark)	(1⁄2)mark

CONFIDENTIAL

In addition to the fittings and apparatus found in a Chemistry laboratory, EACH candidate will require:

1. Solution A,80ml for each candidate
2. Solution C, 80ml for each candidate
3. Solution P,50ml for each candidate
4. Solution Q,60ml for each candidate
5. Solid E, About 1g supplied in a stoppered container.
6. Solid K, About 0.5g supplied in a stoppered container.
7. One Burette, 0-50ml.
8. One 25ml Pipette.
9. Three 250ml Conical Flasks
10. One complete Retort Stand
11. One White Tile
12. One Pipette Filler
13. One Test-tube Rack
14. Six Test-tubes (on a rack)
15. Source of heat
16. Wire gauze
17. Clean metallic spatula
18. Clean glass rod
19. Thermometer with a range of -10°C to 110°C
20. 100cm³ plastic beaker
21. Test tube holder
22. One label
23. Two Boiling tubes
24. Filter funnel
25. Measuring cylinder 10ml
26. Measuring cylinder 50ml
27. Measuring cylinder 100ml
28. Wash bottle filled with distilled water

ACCESS TO

1. Acidified Potassium Manganate (VII) supplied with a dropper.
2. Universal indicator solution supplied with a dropper.
3. PH chart
4. 2M Sodium hydroxide solution supplied with a dropper.
5. Solid sodium carbonate
6. 2M acidified barium nitrate supplied with a dropper.
7. Phenolphthalein indicator

NOTES

1. Solution A is 0.648M hydrochloric acid
2. Solution C is 0.1M hydrochloric acid
3. Solution P is 1M hydrochloric acid
4. Solution Q is 1M sodium hydroxide solution
5. Solid E is Sodium sulphite
6. Solid K is pure Maleic acid