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2024 WAEC Chemistry Practical (a) An aqueous solution of a salt was added to excess sodium sodium trioxocarbonate (IV) solution...

Chemistry
WAEC 2024

(a) An aqueous solution of a salt was added to excess sodium sodium trioxocarbonate (IV) solution in a test tube. There was effervescence, the test tube became warm and a white precipitate was observed. State three inferences that could be drawn from these observations.

(b) Consider the following salts; NH\(_4\)Cl; PbSO\(_4\); NaHCO\(_3\) and Cu(NO\(_3\))\(_2\).

  Select from the list, the salt(s) which:

(i) would not readily dissolve in water;

(ii)produce(s) effervescence with dilute mineral acids;

(iii) decompose(s) on heating;

(iv) dissolve(s) in water to form an alkaline solution;

(v) sublime(s) on heating

(c)  A solution of an acid was titrated with sodium hydroxide solution using methylorange as the indicator. State three precautions that are necessary when carrying out such an experiment.

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Explanation

a(i) Salt solution is acidic

     - Reaction is exothermic.

    - White precipitate is likely to be a trioxocarbonate(IV) salt of Al, Ca and Zn.

    - Prepared solution contained soluble salt of Al, Ca and Zn.       

b(i)PbSO\(_4\)

  (ii) NaHCO\(_3\)

  (iii) NaHCO\(_3\) ; Cu(NO\(_3\))\(_2\).

  (iv) NaHCO\(_3\)

  (v) NH\(_4\)Cl

(c) Precautions to be taken during titration include:

- Wear a lab coat to protect your clothing from spills. 

- Ensure to rinse the burette with an acid solution

- Also ensure the funnel is removed immediately after filling the acid into the burette.

- Avoid error due to parallax while taking the reading to determine the end point.

- Ensure all glassware is clean and free of bubbles. 


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