CHEMISTRY PAPER 3 - 2019 KCSE Prediction Questions Set 2

INSTRUCTIONS

• Answer all the questions 
• All working must be shown clearly where necessary
• Mathematical tables and silent non – programmable electronic calculators may be used
• Candidates may be penalized for not following the instructions given in this paper.
• Candidates must answer the questions in English.

1. You are provided with
   • Solid V
   • 2.0 M hydrochloric acid, solution B
   • 0.1M sodium hydroxide, solution C
   
   You are required to determine the enthalpy change, ∆H for the reaction between solid V and one mole of hydrochloric acid
   
   Procedure I
   Using a burette, place 20 cm³ of 2.0M hydrochloric acid, solution B in a 100ml plastic beaker. Record the temperature of the solution after every half minute and record the values in table 1 below. At exactly 2 ½ minutes, add all of solid V to the acid. Stir the mixture gently with a thermometer and record the temperature of the mixture after every half minute in table 1. Retain the mixture for use in procedure II
   
   Table 1
   

   Time (Min)	0	1	1½	2	2½	3	3½	4	4½	5
   Temperature

   1. On the grid provided, plot a graph of temperature (vertical axis) against time (3mks)                                                                                                                      
      
   2. From the graph, determine the change in temperature ∆T                                          (1mk)
   3. Calculate the heat change for the reaction (Assume that the specific heat capacity of the mixture is 4.2Jk^-1 1g^-1 and the density of the mixture is 1g/cm3.     (1mk)
      
      Procedure II
      Rinse the burette thoroughly and fill it with 0.1 M sodium hydroxide, solution C. Transfer all the contents of the 100ml plastic beaker used in procedure I into a 250ml volumetric flask. Add distilled water to make up to the mark. Label this solution V. Using a pipette and a pipette fillers, pipette 25cm³ of solution V into a conical flask . Add 2-3 drops of phenolphthalein indicator and titrate with solution C. Record your results in table 2 below. Repeat the titration two more times and complete table 2 below.
      

      	I	II	III
      Final burette reading
      Initial burette reading
      Volume of solution C used cm3

      Calculate:                                                                                                                                                                                                                           
      1. The average volume of sodium hydroxide used  (1mk)
      2. The number of moles of;
         1. Sodium hydroxide used     (1mk)
         2. Hydrochloric acid in 25cm³ of solution V   (1mk)
         3. Hydrochloric acid in 250cm³ solution V     (1mk)
         4. Hydrochloric acid in 20cm³ of solution B, that reacted with solid V    (1mk)
         5. Calculate the enthalpy of reaction between solid V and one mole of hydrochloric acid (2mks)
2. You are provided with solid P. Carry out the tests below and record your observations and inferences in the spaces provided
   1. Transfer a spatula and full of solid P into a boiling tube and add 20cm³ of distilled water. Shake thoroughly then filter. Raise the residue and the distilled water and keep both the residue and the filtrate. Divide the filtrate into three portions.
      1. To one portion of the filtrate add ammonia solution drop wise until in excess
         

         Observation	Inference
         1 mk	½ mk

      2. To the second portion, add about four drops of 0.5M lead (II) nitrate solution 
         

         Observation	Inference
         1 mk	1 mk

      3.  To portion three of the filtrate, add 4 drops of Barium chloride solution followed by 5cm³ of nitric (v) acid.
         

         Observation	Inference
         1 mk	1 mk

   2. Scrap the residue from the filter paper in (a) above using a spatula and transfer it into a boiling tube. Add about 8cm³ of 1M nitric (v) acid.
      Keep the resulting solution for use in (c) below
      

      Observation	Inference
      1 mk	1 mk

   3. Divide the solution obtained in (b) above into three portions
      1. To the first portion, add ammonia solution dropwise until in excess
         

         Observation	Inference
         1 mk	1 mk

      2. To the second portion, add 4 drops of 1M hydrochloric acid solution
         

         Observation	Inference
         1 mk	1 mk

      3. To the third portion, add 4 drops of Pottasium iodide solution
         

         Observation	Inference
         ½ mk	½ mk

3. You are provided with solid Q. Carry out the tests below and record you observations and inferences in the spaces provided.
   1. Scoop a portion of the solid using a clean spatula and introduce it to a non-luminous flame.
      

      Observation	Inference
      1 mk	1 mk

   2. To the remaining portion of solid Q, add 10cm³ of distilled water. Shake and divide the solution into three parts.
      

      Observation	Inference
      1 mk	1 mk

   3. To the first portion add about 1cm³ of acidified potassium manganate (vii) solution
      

      Observation	Inference
      1 mk	1 mk

   4. To the second portion, add about 1cm³ of acidified potassium dichromate (vi) solution
      

      Observation	Inference
      1 mk	1 mk

   5. To the third portion, determine the PH of the solution     
      

      Observation	Inference
      ½ mk	½ mk