(a)(i) Define in terms of electron transfer I. oxidizing agent; II. reducing agent.
(ii) Write a balanced equation to show that carbon in a reducing agent.
(iii) State the change in oxidation number of the specie that reacted with carbon in (a)((ii).
(b) A gas X has a vapour density of 32. It reacts with sodium hydroxide solution to form salt and water only. It decolourizes acidified potassium tetraoxomanganate (VII) solution and reacts with H(_2)S to form sulphur. Using the information provided:
(i) identify gas X; (ii) state two properties exhibited by X;
(iii) give two uses of X.
(c) Consider the following substances: sodium; lead (II) iodide; hydrogen; magnesium; oxygen. Which of the substances
(i) conducts electricity?
(ii) is produced at the cathode during electrolysis of H(_2)SO(_{4(aq)})?
(iii) corresponds to the molecular formula A(_2)?
(iv) is an alkaline earth metal?
d)(i) Define the term salt.
(ii) Mention two types of salt
(iii) Give an example of each of the salts mentioned in (d)(ii) above.
(e) In a neutralization reaction, dilute tetraoxosulphate (VI) acid completely reacted with sodium hydroxide solution.
(i) Write a balanced equation for the reaction
(ii) How many moles of sodium hydroxide would be required for the complete neutralization of 0.50 moles of tetraoxosulphate (VI) acid?
Explanation
(a)(i) (1) Oxidation agent is a substance which accepts electrons or is an electron acceptor.
(2) Reducing agent is a substance which donates electrons or is an electron donor.
(ii) 2CuO(_{(s)}) +C(_{(s)}) (to) 2Cu(_{(s)}) + CO(_{2(g)})
H(_{2})O(_{(g)}) + C(_{(s)}) –> CO(_{(g)}) + H(_{2(g)})
CO(_{2(g)}) -> 2CO(_{(g)})
(ii) Cu in CuO from +2 to 0
H in H(_2)O from +1 to 0
C in CO(_2) from +4 to + 2.
(b)(i) X is sulphur (IV) oxide or sulphur dioxide.
(ii)(a) It is heavier than air. (b) It is acidic
(c) Reducing or oxidizing agent.
(d) Colourless (poisonous) gas with irritating smell.
(iii) (1) Used for bleaching
(2) For the manufacture of H(_2)SO(_4)
(3) as germicide and fumigant.
(4) for preservation.
(5) as refrigerant.
(c) (i) sodium magnesium (ii) Hydrogen (iii) Lead(II) iodide (iv) Magnesium.
(d) (i) A salt is a compound formed when all or part of hydrogen of an acid is replaced by metal or ammonium ion.
(ii) (a) Normal salt (b) Acid salt (c) Basic salt (d) Double salt (e) Complex salt.
(iii) NaCl/ZnSO(_4)/NaH(_2)PO(_4)/Zn(OH)Cl/Mg(OH)NO(_3)/NH(_4).Fe(SO(_4))(_2).6H(_2)O).
(e) (I) H(_2)SO(_{4(aq)}) + 2NaOH(_{(aq)}) (to) Na(_2)SO(_4)(_{(aq)}) + 2H(_2)O(_{(l)})
(ii) From the reaction 1 mole of H(_2)SO(_4) = 2 moles of NaOH(_{(l)}).
Therefore 0.50 mole of H(_2)SO(_4) = (frac{2 times 0.5}{1}) of NaOH
= 1 mole of NaOH.