CSEE
Chemistry · Paper 2A · 2025
5 questions 🇹🇿 NECTA ✓ Official NECTA answers
CSEE
🇹🇿 NECTA
✓ Official NECTA answers
Chemistry · Paper 2A · 2025
5 questions
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Questions (5)
Section B
2.
15 marks
A cat has been found dead after consuming a certain solid chemical from opened bottle in the laboratory. It is unfortunate that the bottle label was also destroyed by rats and the investigator decided to name the solid residues as sample T. Carry out qualitative analysis experiments to identify the ions present in the sample which killed the cat based on the following tests:
(i)
Appearance of the sample T.
1 mk
(a)
Prepare a table showing the qualitative analysis results.
10 mk
(a)
Describe the appearance of solid X.
2 mk
(i)
Appearance of the sample T.
1 mk
(b)
Identify the cation and the anion in the solid.
4 mk
(ii)
Action of heat on the sample T.
2 mk
(ii)
Action of heat on the sample T.
3 mk
(b)
Heat about 1 cm³ of solid X in a hard glass test tube.
4 mk
(c)
Write the chemical formula of the solid.
3 mk
(c)
Dissolve about 1 g of solid X in 5 cm³ of distilled water and test the solution with litmus paper.
3 mk
(iii)
Solubility of the sample T.
1 mk
(iii)
Solubility of the sample T.
2 mk
(d)
Write a balanced chemical equation for the reaction in experiment (ii).
5 mk
(d)
To about 2 cm³ of the solution obtained in (c), add a few drops of aqueous ammonia.
4 mk
(iv)
Action of dilute hydrochloric acid on the solid sample T.
2 mk
(iv)
Action of dilute hydrochloric acid on the solid sample T.
3 mk
(e)
To about 2 cm³ of the solution obtained in (c), add a few drops of barium chloride solution followed by a few drops of dilute hydrochloric acid.
4 mk
(v)
Action of concentrated sulphuric acid on the solid sample 'T.
3 mk
(e)
Write two uses of sample T in daily life.
3 mk
(v)
Action of concentrated sulphuric acid on the solid sample 'T.
2 mk
(vi)
Action of aqueous sodium hydroxide on the solution sample T.
2 mk
(f)
To about 2 cm³ of the solution obtained in (c), add a few drops of silver nitrate solution.
4 mk
(vi)
Action of aqueous sodium hydroxide on the solution sample T.
3 mk
(g)
Identify the cation and anion present in solid X.
3 mk
(vii)
Action of barium chloride on the solution sample T.
3 mk
(vii)
Action of barium chloride on the solution sample T.
2 mk
(viii)
Do confirmatory test for the cation and anion.
7 mk
((viii)
Do confirmatory test for the cation and anion.
3 mk
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Section E
1.
0 marks
(i)
the molarity of N.
2 mk
(a)
What is the colour change of the reaction?
1 mk
(a)
What is the colour change of the reaction?
1 mk
(b)
What volume of the acid required for complete reaction with the carbonate?
2 mk
(b)
What volume of the acid required for complete reaction with the carbonate?
1 mk
(ii)
the molarity of D.
3 mk
(c)
Identify the type of reaction in this experiment.
1 mk
(iii)
the molecular weight of the carbonate.
2 mk
(c)
Identify the type of reaction in this experiment.
1 mk
(iv)
the atomic mass of the monovalent metal in the carbonate.
3 mk
(d)
Write a balanced chemical equation for the reaction between D and N.
2 mk
(d)
Write a balanced chemical equation for the reaction between D and N.
3 mk
(e)
16 mk
(e)
Calculate:
7 mk
(f)
Write the ionic symbol for the metal in D.
3 mk
(f)
Write the ionic symbol for the metal in D.
2 mk
(g)
Suggest another indicator that could be used for this titration and justify your choice.
3 mk
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