Number 1
Number 2
Please TABULATE YOUR ANSWERS;
(2a)
Test: F + 10 cm³ distilled water, filter.
Test filtrate with litmus
Observation: Dissolves partially. Filtrate turns red litmus blue / blue litmus stays blue
Inference: Solution is alkaline; presence of alkaline salt e.g. Na₂SO₄ or similar
(2bi)
Test: Filtrate + zinc dust
Observation: Effervescence / bubbles produced; colourless gas
Inference: Possible reduction reaction; H₂ gas evolved
(2bii)
Test: Filtrate + NH₃(aq) in drops then excess
Observation: White precipitate forms, dissolves in excess
Inference: Cu²⁺ ions present. Forms deep blue complex in excess
(2biii)
Test: Filtrate + BaCl₂(aq) + dilute HCl
Observation: White precipitate insoluble in HCl
Inference: SO₄²⁻ ions present
(2ci)
Test: Residue + 3 cm³ distilled water, boil
Observation: Residue partially dissolves, forms a paste/suspension
Inference: Insoluble carbohydrate starch present
(2cii)
Test: Mixture from (c)(i) + iodine solution
Observation: Blue-black colouration
Inference: Starch confirmed
Conclusion:
(i)The inorganic salt is CuSO₄ copper(II) tetraoxosulphate
(ii)The carbohydrate is starch
Number 3
(3ai)
(i)Guarantees accurate volume measurement.
(ii)Ensures alignment with the bottom of the meniscus.
(iii)To prevent parallax error
(3aii)
(i)Avoids false titration calculations
(ii)Dropping liquid changes the initial volume measurement.
(iii)Prevents remaining liquid from dripping into the burette.
(3aiii)
(i)Maintains the exact concentration (molarity).
(ii)Prevents dilution of the acid.
(iii)Removes residual water or contaminants.
(3b)
(i)Beaker or Funnel
(ii)Analytical balance (or weighing balance)
(iii)Volumetric flask
COMPLETED!!!