(a)(i) Describe briefly how trioxonitrate (V) ions could be tested for in the laboratory.
(ii) State two uses of each of the following compounds: I. sodium chloride; II. sodium trioxocarbonate (IV).
(b) Write balanced equations for the reactions involved in the extraction of iron in the blast furnace.
(ii) State Faraday’s first law of electrolysis.
(iii) State two applications of electrolysis.
(c) Concentrated tetraoxosulphate (VI) acid is added to sugar crystals in a beaker. State what would be observed. Explain briefly your answer.
(d) Write an equation for the reaction of zinc powder with:
(i) dilute tetraoxosulphate (VI) acid;
(ii) concentrated tetraoxosulphate (VI) acid.
(e) What property of concentrated tetraoxosulphate (VI) acid is shown in (d)(ii)
Explanation
(a)(i)
| Test | Observation | |
| i. | Sample of concentrated H\(_2\)SO\(_4\) + heat |
Brown fumes of NO\(_2\) evolved |
| ii. | Sample + Copper + cone H\(_2\)SO\(_4\) and warm |
Reddish brown fume of NO\(_2\) |
| iii. | Cold Sample solution + freshly prepared FeSO\(_4\) solution and followed by conc H\(_2\)SO\(_4\) (few drops) to the sample solution + freshly prepared FeSO\(_4\) in slant form |
A brown ring observed between the junction of the acid and sample solution. |
(ii) Two uses of each of the following compounds:
(1) Sodium Chloride - food seasoning, food preservative, glazing pottery/earthen ware. soap production, crude oil refilling, water softener, production of chlorine/hydrogen/ sodium metal, NaOH/NaClO\(_3\)/NaOCl/Na\(_2\)CO\(_3\) lowering melting point of ice preparation of freezing mixture. Used in tannery industry/tanning.
(2) Uses of sodium trioxocarbonate (IV) - Manufacture of glass/borax in detergents/ soaps, manufacture of paper softening hardwater, manufacture of NaOH treating (concentrated) acid splash, standardization of acids/analytical reagent.
(b)(i) Balanced equations for the reactions involved in the extraction of iron in the blast furnace.
C\(_{(g)}\) + O\(_{2(g)}\) ----> CO\(_{2(g)}\)
CO\(_{2(g)}\) + C\(_{(g)}\) --> 2CO\(_{(g)}\)
Fe\(_{2}\)O\(_{3}\) + 3CO\(_{(g)}\) \(\to\) 2Fe + 3CO\(_{2(g)}\)
CaO + SiO\(_{2}\) -> CaSiO\(_{3}\)
CaCO\(_{3}\) -> CaO + CO\(_{2}\)
(ii) Faraday's first law of electrolysis states that the mass of an element discharged at the electrode is directly proportional to the quantity of electricity passed through the electrolyte.
(iii) Two applications of electrolysis are: Electroplating of metals, Extraction of metals, Purification of metals, Preparation of compounds/elements, Production of gases H\(_{2}\), O\(_{2}\), Cl\(_{2}\) (any 2)
(c) Sugar crystals + concentrated H\(_{2}\)SO\(_{4}\) in a beaker. Observations are as follows:
(1) Concentrated acid dehydrates the sugar.
(2) A mass of carbon/black soot/ sugar charcoal is formed.
(3) Reaction is exothermic (heat evolved or released).
(d) Equations for the reaction of Zinc powder with dilute tetraoxosulphate (VI) acid:
(i) Zn\(_{(g)}\) + H\(_{2}\)SO\(_{4(aq)}\) -> ZnSO\(_{4(aq)}\) + H\(_{2(g)}\)
(ii) Reaction with dilute concentrated H\(_2\)SO\(_4\)
(iii) Zn\(_{(g)}\) + 2H\(_2\)SO\(_{4(aq)}\) -> ZnSO\(_{4(aq)}\) + SO\(_{2(g)}\) + 2H\(_2\)O\(_{(l)}\)
(e) Property of concentrated tetraoxosulphate (VI) acid shown in (d)(1) is oxidizing property.