Question

4(a)(i) In the laboratory preparation of dry chlorine gas, state the: I. reagents used; II. drying agents used; III. mode of collection. (b)(i) Name the main raw materials used for extraction of iron in the blast furnace. (ii) Write the equations of the reactions taking place in the blast furnace. (iii) What is the name given to the iron obtained directly from the blast furnace? (iv) State why the iron named in 4(b)(iii) have a relatively low melting point? (c) The following equation represents one of the reaction steps involved in the contact process: 2SO2(g) + O2(g) <=> 2SO3(g), (Delta)H=-395.7 kJ mol^-1. (i) Why is SO3 produced during the reaction not dissolved directly in water to form H2SO4? (ii) Why is H2SO4 regarded as a heavy chemical? (iii) State the property exhibited by tetraoxosulphate (IV) acid in each of the following reaction equations: I. Pb(NO3)2(aq) + H2SO4(aq) -> PbSO4(aq) + 2HNO3(aq); II. H2S(g) + H2SO4(aq) -> S(s) + 2H2O(l) + SO2(g). (d) Write a balanced chemical equation for the reaction between propanol and sodium.

Accepted Answer

(a)(i) I. Reagents used in the laboratory preparation of dry chlorine gas: Hydrochloric acid and manganese (IV) oxide. II. Drying agent used: Concentrated H2SO4. III. Mode of collection: it is collected by downward delivery or upward displacement of air.
(b)(i) Main raw materials used for extraction of iron in the blast furnace: coke; Iron ore; Limestone.
(ii) Equations of reactions in the blast furnace: C+O2->CO2; C+CO2->2CO; Fe2O3+3CO->2Fe+3CO2; CaCO3 --(heat)--> CaO+CO2; CaO+SiO2->CaSiO3.
(iii) The iron obtained directly from the blast furnace is known as pig iron.
(iv) Pig iron has a relatively low melting point because it contains a high amount of carbon (as impurity).
(c)(i) It is because the direct dissolution of SO3 in water will release a huge amount of heat that can boil the acid formed and consequently cause a splash.
(ii) H2SO4 is regarded as a heavy chemical because it is produced and required in large quantities.
(iii) I. Precipitating agent. II. Oxidizing agent.
(d) 2C3H7OH + 2Na -> 2C3H7ONa + H2.

WAEC Chemistry 2020 Theory — Question 4

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