Question

2(b) When Titanium chloride was electrolysed by passing a 0.12A current through the solution for 500 seconds, 0.015g of titanium was deposited. What was the charge on the titanium ion? [IF=96500 C, Ti=48.0]
(c)(i) Aluminium can be obtained by the application of electrolysis. State the electrolyte which yields aluminium on smelting.
(ii) Name two major factors which would favour the siting of an aluminium smelter in a country.
(d)(i) Define the term paramagnetism.
(ii) Consider the following ions: 24Cr³⁺, 24Cr⁶⁺.
(I) Deduce the number of unpaired electrons in each of the ions.
(II) State which of the ions will have a greater power of paramagnetism.
(III) Give a reason for the answer stated in 2(d)(ii)(II).

Accepted Answer

(b) Given: I = 0.12A, t = 500s, m = 0.015g, M(Ti) = 48.
Quantity of electricity, Q = It = 0.12 × 500 = 60C.
Using m/M = Q/(nF): n = MIt/(mF) = (48 × 0.12 × 500)/(0.015 × 96500) = 2880/1447.5 ≈ 1.99 ≈ 2.
Charge on the titanium ion = +2.

(c)(i) The electrolyte which yields aluminium on smelting is alumina (Al2O3) mixed with molten cryolite (Na3AlF6).
(ii) Factors favouring siting of an aluminium smelter: availability of raw material (i.e. abundant deposits of bauxite); availability and cheap source of electricity.

(d)(i) Paramagnetism refers to a phenomenon whereby some materials are weakly attracted by an externally applied magnetic field, due to the presence of one or more unpaired electrons which are attracted by the magnetic field.
(ii)(I) 24Cr³⁺ has the electronic configuration 1s²2s²2p⁶3s²3p⁶3d³ i.e. [Ar]3d³ — 3 unpaired electrons.
24Cr⁶⁺ has the electronic configuration 1s²2s²2p⁶3s²3p⁶ i.e. [Ne]... wait — 24Cr⁶⁺ = [Ar] with 3d⁰4s⁰ — 0 unpaired electrons.
(II) 24Cr³⁺ has the greater power of paramagnetism.
(III) This is because 24Cr³⁺ has a greater number of unpaired electrons (3d³) than 24Cr⁶⁺ (which has no unpaired electrons in its 3d orbital); the greater the number of unpaired electrons, the greater the paramagnetism.

WAEC Chemistry 2022 Theory — Question 3

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