(a)Define the term solubility.
(b) The table below gives the solubility of salt Z at various mperatures
|
Temperature (°C) |
0 | 10 | 20 | 30 | 40 | 50 | 60 |
|
Solubility (mol dm(^{-3})) |
0.13 | 0.21 | 0.31 | 0.45 | 0.63 | 0.85 | 1.10 |
(i) Plot a graph of solubility against temperature.
(ii) From the graph determine the solubility of salt Z at 35°C.
(iii) If 100cm(^{-3}) of the saturated solution is cooled from 55°C to 35°C, calculate the mass of salt Z that would crystallize out. [Molar mass of salt Z = 100 g]
(c)(i) Write a balanced equation to illustrate the reaction of AI(_2)O(_3) with dilute I. HCI; II. NaOH.
(ii) What is the name given to an oxide that exhibits both acidic and basic properties?
(iii) Give one metallic oxide which exhibite these properties.
(d)(i) Determine the oxidation number of: I. Al in [Al (H(_2)O)(_6)](^{3+}); II. H in NaH.
(ii) Give the IUPAC name of each of the following substances; I. CuSO(_4).5H(_2)O; II. CaCO(_3); Ill. KMnO(_4).
Explanation
(a) Solubility is the maximum amount of solute that would dissolve / be contained in 1 dm(^3) of solution at a given temperature.
(b)(i)
(ii) At 35° solubility = 0.50 to 0.55 moldm(^{-3}) range
(iii) Solubility @ 55°C = 0.95 to 0.98 moldm(^{-3})
1 moldm(^{-3}) of salt Z = 0.97; 100 = 97g
100cm(^{-3}) will contain = (frac{97 times 100}{100}) = 9.7g
Solubility @ 35°C = 0.54moldm(^{-3})
1 drn(^{-3}) contain = 0.54 x 100 = 54g
100cm(^{-3}) will contain 54 x100 = 5.4g
10 Mass of salt that would crystallize out = 9.7 – 5.4 = 4.3g
(c)(i) (I) Al(_2)O(_{3(s)}) + 6HCl(_{(aq)}) (to) 2AlCl(_{3(s)}) + 3H(_2)O(_{(l)})
(II) Al(_2)O(_{3(g)}) 2NaOH(_{(aq)}) + 3H(_2)O(_{(l)}) (to) 2NaAl(OH)(_4)
(ii) Amphoteric
(iii) ZnO / PbO / SnO /Al(_2)O(_3)
d)(i) I [Al(H(_2)O)(_6)](^{3+}) = x + (0) = +3
x = +3
Al = +3
(II) NaH = 1+ x = 0
x = —1
H = — 1
(ii)(I) Copper (II) tetraoxosulphate VI pentahydrate
(II) Calcium tripxocarbonate IV
(III) Potassium tetraoxomanganate VII.