KAKAMEGA EAST DISTRICT CHEMISTRY PRACTICAL QUESTIONS

KAKAMEGA EAST DISTRICT CHEMISTRY PRACTICAL QUESTIONS

CONFIDENTIAL

INSTRUCTIONS

Each candidate should be provided with the following:-

• Burette
  
• Pipette
  
• Two conical flasks
  
• Funnel
  
• Phenolphthalein indicator
  
• Methyl orange indicator
  
• Universal indicator
  
• Solution a 100cm³
  
• Solution b 100cm³
  
• Solution c 100cm³
  
• Distilled water in wash bottle
  
• 0.2m CuSO₄ (solution Y)
  
• 0.7g zinc powder (solid Z)
  
• Thermometer
  
• 100ml plastic beaker
  
• Stop watch or wrist watch
  
• Tissue paper ½ metre
  
• 6 test tubes
  
• One boiling tube
  
• Solid P
  
• Solid Q
  
• Filter paper
  
• Means of heating
  
• 2m NaOH
  
• 2m H₂SO₄
  
• 0.1m bacl₂
  
• 0.1m pb(no₃)₂
  
• 2m HCl
  
• 2m NH_3(aq)
  
• Metallic spatula
  
• 0.5g NaHCO₃
  

  Notes on preparation of solutions :-  
  

  • Solution A 0.05M sodium Carbonate
    
  • Solution B = 0.1M of HCl
    
  • Solution C = 0.16g KOH + 1.94g KCl in 250cm³ solution
    
  • Solid P = CaCl₂ and MgCO₃
    
  • Solid Q = Carboxylic acid (oxalic)
    

1.  You are provided with:-

• Solution A containing 0.05 moles in 1dm³ of solution of anhydrous Sodium Carbonate
• Solution B, monobasic acid, HX
• Solution C, 2.1g of a mixture of potassium hydroxide (KOH) and potassium chloride (KCl) dissolved in distilled water and made up to 250cm³ solution.  

You are required to:

1. Standardise the monobasic acid, solution B
2. Determine the percentage of potassium chloride (KCl) in the mixture.

Procedure:

Fill the burette with solution B. Pipette 25.0cm³ of solution A into a clean dry conical flask

and titrate with solution B using methyl orange indicator. Record your results in table 1 below:-

123Final burette reading (cm3)Initial burette reading (cm3)Volume of solution B used (cm3)
(a) Calculate the average volume of solution B used
(b) Given that the equation for the reaction taking place is:-
Na2CO3(aq) + 2HX(aq) 2NaX(aq) + CO2(g) + H2O(l)
 Calculate the concentration of solution B in moles per litre
Procedure II
Fill the burette to the 0.0mark with solution B. Pipette 25.0cm3 of solution C into a clean
dry conical flask and titrate it against solution B using phenolphthalein indicator. Repeat the
titration and fill table II below:-
Table II
123Final burette reading (cm3)Initial burette reading (cm3)Volume of solution B used (cm3)

 (c)What is the average volume of solution B used?
 (d) Calculate the concentration of solution C in :-
  (i) Moles per litre  
  (ii) Grams per litre (K=39, O=16, H=1)  
(e) Calculate the percentage of potassium chloride in the mixture  
2.  You are provided with:-
Solution Y containing 0.2moles of copper (II) sulphate per litre of solution
Solid Z  
 

You are required to:

Determine the heat evolved when 1 mole of solid Y reacts with solid Z

Procedure

• Measure 40cm³ of solution Y and place it into an insulated 100cm³ plastic beaker
• Stir the solution with the help of thermometer and record its temperature after every ½ minute

for 1½ minutes.

• After exactly 2 minutes, add all the solid Z provided and continue stirring the mixture while recording the temperature of solution and complete the table below:

 (b) (i) On the graph paper provided, plot a graph of temperature against time

  (ii) From your graph, determine the maximum temperature change

(c) Given that the density of the solution is 1g/cm³, determine the quantity of heat evolved

when 40cm³ of solution Y is reacted completely with solid Z

(specific heat capacity of solution = 4.2jg^-1k^-1)

(d) (i) Given that solid Z is Zinc powder, write an ionic equation of the reaction which occurs

  (ii) Determine the moles of copper ions used up in the reaction  

  (iii) Determine the amount of heat that would be evolved if one mole of Copper

(II) ions were used up

  (iv) Explain why the value obtained in this reaction is lower than the actual value?  

3.  I. You are provided with solid P. Carry out the tests below and write the observations

and inferences in the spaces provided  

(a) Heat about one third of solid P in a clean dry test tube

 (b) Add 10cm³ of distilled water to the remaining solid P in a boiling tube and shake.

Filter and retain both the residue and the filtrate. Divide the filtrate into four portions

  (i) To the first portion add aqueous Sodium hydroxide drop by drop till in excess

(ii) To the second portion add dilute sulphuric acid

(iii) To the third portion, add barium chloride solution

  (iv) To the fourth portion, add Lead (II) nitrate solution

(c) (i) To the residue from (b) above in the test-tube, add dilute hydrochloric acid and retain

the mixture  

  (ii) To the mixture is(c)(i) above, add aqueous ammonia drop wise till in excess

II. You are provided with solid Q. Carry out the test below and write your observations and

inferences in the spaces provided  

1. Scoop a little of solid Q with a clean dry metallic spatula and ignite using a Bunsen flame.

1. Place the remaining solid Q in a boiling tube. Add about 10cm³ of distilled water. Shake the

mixture until it dissolves. Divide the solution into 4 portions  

(i) To the first portion, test the PH with PH paper.

(ii) To the second portion, add solid sodium Carbonate and shake