(a) State Gay Lussac’s Law.
(b) Carbon (II) oxide reacted with oxygen to form carbon (IV) oxide in a see tube.
(i) Write a balanced equation for the reaction.
(ii) If 40 cm(^3) of the carbon (II) oxide were mixed with cm(^3) of oxygen,
I. calculate the volume of carbon (IV) oxide produced
II. which reactant is in excess and how much?
III. what was the total volume of the gaseous mixture at the end of the reaction?
(c) Consider the following oxides: CaO, SiO(_2), CO, NO(_2) and ZnO. Which of the oxide(s)
(i) is an acidic oxide that is insoluble in water?
(ii) reacts with water to give alkaline solution?
(iii) is amphoteric?
(iv) is neutral?
(v) is/are gaseous at room temperature?
(d) Explain why
(i) colourless concentrated trioxonitrate (V) acid turns yellow,
(ii) dilute trioxonitrate (V) acid does not liberate hydrogen when it reacts with magnesium.
(e) Write a chemical equation for the thermal decomposition of (i) Cu(NO(_3))(_{2(g)})
(ii) NH(_4)NO(_{3(g)})
Explanation
a) Gay Lussac’s law states that when gases react, they do so in volumes which simple ratios to one another and to the volumes of the products, if gaseous, provided that the temperature and pressure remain constant.
(b) (i) 2CO(_{(g)}) + O(_{2(g)}) (to) 2CO(_{2(g)})
(ii) I. from the equation: 2 volumes of CO(_{(g)}) and 1 volume of O(_{2(g)}) —> 2 volumes of CO(_2). ratio of reacting volumes
40cm(^3) + 20cm(^3) —> 40cm(^3)
40cm(^3) of CO requires 20cm(^3) of oxygen to form 40cm(^3) of CO(_2).
40cm(^3) of CO(^2) is produced
II. excess reactant is oxygen Volume is 30cm(^3)— 20cm(^3) = 10cm(^3).
III. total volume of gaseous mixture 10cm(^3) of O(^2) + 40cm(^3) CO(_2) = 50cm(^3).
(c) (i) SiO(_2). (ii) CaO (iii) ZnO (iv) CO (v) CO and NO(_2).
(d) (i) Conc. HNO(_3). slowly decomposes releasing brown NO, which dissolves in the acid to give the yellow colour.
(ii) HNO(_3). is an oxidizing acid. Any hydrogen produced is oxidized to water.
(e) (i) 2Cu(NO(_3))(_2) (to) 2CuO(_{(s)}) + 4NO(_{2(g)}) + O(_{2(g)})
(ii) NH(_4)NO(_3{(s)}) (to) N(_2)O(_{(g)}) + 2H(_2)O(_{(g)})