TEST OF PRACTICAL KNOWLEDGE QUESTION (a) A zinc salt, E when heated strongly, produced a brown gas with pungent smell, a colourless gas that rekindled a glo...

Answer Details

(a)

1. (i) The salt E is likely to be Zinc sulfide (ZnS).
2. (ii) The equation for the decomposition of Zinc sulfide (ZnS) is:
   2 ZnS (s) -> 2 Zn (s) + S₈ (g)
3. (iii) When the residue is allowed to cool, a white solid would be observed. This solid would be Zinc (Zn).

(b)

To prepare 250cm³ of 0.2 mol dm³ H₂SO₄ from 150 cm³ of a 1.0 mol dm³ stock solution of the acid, you would need to dilute the stock solution. You can do this by adding 150 cm³ of the 1.0 mol dm³ stock solution to an equal amount of water, which would give you 300 cm³ of a 0.5 mol dm³ solution. Then, you could add 50 cm³ more of water to the solution, which would give you a final volume of 350 cm³ of a 0.2 mol dm³ solution of H₂SO₄.

(c)

The aqueous solution of Al₂(SO₄)₃ has a neutral effect on litmus paper. It does not turn red litmus paper blue or blue litmus paper red, indicating that it is a neutral solution.