THE UNITED REPUBLIC OF TANZANIA

PRESIDENT’S OFFICE REGIONAL ADMINISTRATIN AND LOCAL GOVERNMENT

IRINGA DISTRIC COUNCIL

FORM IV PRE-MOCK EXAMINATION MAY 2021

032 CHEMISTRY 2A

(ACTUAL PRACTICAL A)

INSTRUCTIONS:

  1. This paper consists of two questions.
  2. Answer all question
  3. Qualitative Analysis Guidance Pamphlets may be used after a thorough check by the supervisor.
  4. Each question carries 25 marks
  5. Write your examination number on every page of your answer booklet(s)
  6. You may use the following constant:

Atomic masses:

H=1, C=12, O=16, K=39,

1litre=1dm3=1000cm3

 

  1. You are provided with the following solutions:

    U: 0.05M sulphuric acid solution.

    T: Containing 1.4g of metal hydroxide (YOH) dissolved in 250cm3 of the solution.

    M.O: Methyl orange.

    Procedures:

  2. Put solution U into the burette, pipette 25cm3 or 20cm3 of solution T into titration flask. Put two to three drops of methyl orange into the titration flask. Titrate solution U from the burette against solution T in the titration flask until colour change is observed. Note the burette readings. Repeat the procedures to obtain three more readings in a tabular form.

    QUESTIONS:

  3. (i)…………cm3 of T required ………….cm3 of U for complete reaction.

    (ii)The colour change at end point was from…………………to …………………….

  4. (i)Write a balanced chemical and ionic equation for the reaction between solution U and T.

    (ii)State a reason to why methyl orange indicator is used.

    (iii)State which solution is titrant and analyate.

  5. Calculate the molarity of solution T in,

    (i)mol/dm3 (ii) g/dm3

  6. Calculate

    (i)the molar mass of metal hydroxide YOH

    (ii)the atomic mass of Y

    (iii) name element Y

  7. Mention two application of volumetric analysis in medicine.

     

  8. You are provided with the following:

    A: Containing 1M sodium thiosulphate (Na2SO4)

    B: Containing 0.1M Nitric acid (HNO3)

    C: Distilled water,

    Piece of paper

    Stop-watch

    Procedure

    1. Using measuring cylinder measure 5cm3 of solution A and put 100cm3 beaker.
    2. Measure 5cm3 of solution B and put into 100cm3beaker containing solution A and immediately start the stop- watch.
    3. Swirl the contents in the 100cm3 beaker and put the beaker on the top of mark X on piece of the ‘paper. Watch the mixture from the above and observe changes.
    4. Switch off the stop –watch when the mark X disappear.
    5. Record the time taken for the later X to disappear.
    6. Repeat procedures (i) to (v) using the data shown in Table 1.

     

    Table1

Experiment

Volume of B cm3

Volume of A cm3

Volume of Distilled water cm3

Time (s)

1

5

5

0

 

2

5

4

1

 

3

5

3

2

 

4

5

2

3

 

 

 

QUESTIONS.

  1. What is the aim of the whole experiment?
  2. Complete Table1
  3. With state symbols, write the balanced chemical for the reaction between A and B.
  4. Which the substance was produced during the reaction which obscured letter X?
  5. Why did the cross X disappear?
  6. Write two main allotropes and two uses of the product which obscured the cross X
  7. Plot the graph of volume of A ( Na2S2O3) solution against time (s)

 

 

 

 

 

 

 

 


 

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