Waec Chemistry 2000 Past Questions and Answers

Question 51:

• WAEC 2000

(a)(i) Give the names of two allotropes of sulphur.
(ii) State and explain what is observed when hydrogen sulphide is bubbled through acidified potassium tetraoxomanganatc (VII) solution
(iii) List one product of the reaction of sulphur (IV) oxide with hydrogen sulphide

(b)(i) What are the raw materials for the manufacture of tetraoxosulphate (VI) acid by the contact process?
(ii) Write an equation for the reaction that requires a catalyst in the contact process and state the catalyst used.
(iii) State the observation and the product formed when concentrated H\(_2\)SO\(_4\) reacts with each of the following:
I. Copper turnings Ii. A cube of sugar

(c)(i) Give three uses of sodium trioxocarbonate (IV).
(ii) What name is given to reactions of the following type?:
exposure to air
Na\(_2\)CO\(_3\) + 10H\(_2\)O\(_{(s)}\) \(\to\) Na\(_2\)CO\(_3\); H\(_2\)O\(_{(S)}\) + 9H\(_2\)O
(iii) Calculate the solubility of Na\(_2\)CO\(_3\) at 25°C, if 2.0 cm\(^3\) of its saturated solution at that temperature gave 1.75g of the anhydrous alt. [C = 12, O = 16, Na = 23].