(a)(i) What are acidic oxides?
(ii) Give one example of each of the following oxides: I. acidic oxide; II. basic oxide; III. amphoteric oxide; IV. neutral oxide
(b)(i) Define each of the following terms; I. Heat II. Heat of neutralization
(ii) Weite the above an equation to illustrate each of the terms in (b)(i) above
(ii) Given that the standard heat of combustion of butane (C\(_4\)H\(_{(10)}\) is + 5877 kJmol\(^{-1}\), calculate the heat of 14.5 g butane. [ H = 1, = 12 ]
(c) (i) Name two allotropes of sulphur
(ii) State one difference between the two allotropes.
(d)(i) Give two characteristics of noble eases
(ii) State one use each of I. He; II. Ar.
(e) State what is observed on warming ammonium trioxonitrate (V) with sodium hydroxide.
Explanation
(a)(i) Oxide of non-metals which dissolve in water to form acidic solution.
(ii) 1. Acidic oxides:- SO\(_2\)/CO\(_2\)/NO\(_2\), etc.
2. Basic oxides:- CaO/Na\(_2\)O/K\(_2\)O, etc.
3. Amphoteric oxides:- Al\(_2\)O\(_3\)/ZnO/PbO, etc.
4. Neutral oxides:- CO/N\(_2\)O, etc.
(b)(i) Heat of combustion is the heat change when one mole of a substance is completely burnt in oxygen or burnt in excess oxygen
(ii) Heat of neutralization is the heat change when one mole of water is produced as a result of a reaction between an acid and alkali in dilLte solution or the heat change when one mole of H+ from an acid reacts with one mole of OH\(^-\) from an alkali to form one mole of H\(_2\)O.
(ii)1. C\(_{(g)}\) + O\(_{2(g)}\) \(\to\) CO\(_{2(g)}\)
2. HaOH\(_{(aq)}\) + HCl\(_{(aq)}\) \(\to\) NaCI + H\(_2\)O\(_{(l)}\) \(\Delta\) Hn\(^o\)
3. Molar mass of C\(_4\)H\(_{10}\) = 12 x 4 + 1 x 10
= 48 + 10 = 58g mol\(^{-1}\) .
58g of C\(_4\)H\(_{10}\) = 5877kJ mol\(^{-1}\)
14.5 of C\(_4\)H\(_{10}\) = \(\frac{5877 \times 14}{58}\) kJ mol\(^{-1}\)
= + 1469.25 kJ.
(c)(i) Rhombic
Monoclinic
|
Rhombic |
Monoclinic |
|
Yellow translucent crystal |
Transparent amber crystal |
|
Stable at temperature below 96°C |
Unstable at temperature below 96°C |
|
Higher density than monoclinic |
Lower density than rhombic |
|
Lower melting point |
Higher melting point |
|
Octahedral shaped |
Needle shaped. |
(d)(i)(a) They are monoatomic gases
(b) They are chemically unreactive
(c) Have low melting/boiling point.
(ii) He — filling balloons. Ar — arc welding.