State what you would see on; (i)… | Chemistry

Question 1 Report

State what you would see on;

(i) bubbling SO\(_2\) into acidified KMnO\(_4\) solution

(ii) mixing zinc dust with CuSO\(_4\) solution

(iii) adding concentrated HNO\(_3\) to freshly prepared FeSO\(_4\) solution.

(b) List two substances in case which, if added to dilute H\(_2\)SO\(_4\), would give you

(i) H\(_{2(g)}\)

(ii) ZnSO\(_{4(aq)}\)

(c)

The diagram labelled I to IV below illustrate different laboratory set-ups used in the separation of mixtures.

(i) Name the separation technique illustrated by each diagram

(ii) Which of the set-ups is used for concentrating dilute salt solutions, for the purpose of crystallization?

(iii) Which of the set-ups is used in obtaining clear water from muddy water?

(iv) Mention the set-up you would use to separate a polar solvent from a non-polar solvent

(v) State the modification you would make to the set-up labelled IV in order to use it for separating a mixture of NaCl and NH\(_4\)CI

Answer

Answer Details

(a) Observations

(i) SO₂ bubbled into acidified KMnO₄: the purple (pink) solution is decolourised, becoming colourless. SO₂ reduces the tetraoxomanganate(VII).
(ii) Zinc dust with CuSO₄ solution: the blue colour of the solution gradually fades until it becomes colourless, and a reddish-brown (pink) deposit of copper is formed.
(iii) Concentrated HNO₃ added to freshly prepared FeSO₄ solution: the solution changes colour from green to brown as Fe²⁺ is oxidised to Fe³⁺.

(b) Substances added to dilute H₂SO₄

(i) To give H₂(g): magnesium and zinc (iron is also acceptable).
(ii) To give ZnSO₄(aq): zinc oxide (ZnO) and zinc trioxocarbonate(IV) (ZnCO₃); zinc metal is also acceptable.

(c) Separation set-ups I to IV

(i) Techniques: I - Filtration; II - Chromatography; III - Use of a separating funnel (solvent extraction); IV - Evaporation.
(ii) Concentrating a dilute salt solution for crystallisation: set-up IV (evaporation).
(iii) Obtaining clear water from muddy water: set-up I (filtration).
(iv) Separating a polar solvent from a non-polar solvent: set-up III (the separating funnel).
(v) Modifying set-up IV to separate NaCl and NH₄Cl: cover the evaporating dish with an inverted funnel and heat. The NH₄Cl sublimes and re-solidifies on the cool funnel, leaving NaCl in the dish.

State what you would see on; (i) bubbling SO\(_2\) into acidified KMnO\(_4\) solution (ii) mixing zinc dust with CuSO\(_4\) solution (iii) adding concentrat...