(a)(i) Define the first ionization energy of an element
(ii) Consider the following table and use it to answer te question that follows
| Element |
Li |
Be |
b |
C |
N |
O |
F |
Ne |
| Atomic number |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
| 1st I.E/kj mol?1
|
520 |
900 |
801 |
1086 |
1402 |
1314 |
1681 |
2081 |
Explain briefly why the first ionization energy of B is less than that of Be despite the fact that the atomic number of B is greater than that of Be.
(b) When Titanium chloride was electrolysed by passing 0.12 A current through the solution for 500 seconds, 0.015 g of titanium was deposited. What is 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 electrolysis.
(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: 24Cr2+
, 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
(l) Give a reason for the answer stated in (d)(ii)(II)
(a)(i) The first ionization energy of an element is the amount of energy required to remove one electron from a neutral atom of that element in the gaseous state.
(ii) The missing value in the table is 730 kJ mol⁻¹ for the first ionization energy of lithium (Li).
Explanation for (a): The first ionization energy of B is less than that of Be because B has an electron in a p-orbital, which is further away from the nucleus than the s-orbital electrons in Be. As a result, the attraction between the nucleus and the outermost electron is weaker in B than in Be, making it easier to remove an electron from B.
(b) The amount of charge on the titanium ion can be calculated using the formula:
Charge = (Current x Time x IF) / Mass
where IF is the Faraday constant and equals 96500 C mol⁻¹.
Plugging in the values given, we get:
Charge = (0.12 A x 500 s x 96500 C mol⁻¹) / 0.015 g
Charge = 1.934 x 10⁶ C mol⁻¹
Since the charge on a single titanium ion is 4+, we can calculate the number of moles of titanium deposited by dividing the mass by the molar mass:
n(Ti) = 0.015 g / 48.0 g mol⁻¹ = 3.125 x 10⁻⁴ mol
Dividing the total charge by the number of moles of titanium gives us the charge on a single titanium ion:
Charge on Ti⁴⁺ ion = (1.934 x 10⁶ C mol⁻¹) / (3.125 x 10⁻⁴ mol) = 6.188 x 10⁹ C
(c)(i) The electrolyte which yields aluminium on electrolysis is molten cryolite (Na₃AlF₆) mixed with aluminium oxide (Al₂O₃).
(ii) Two major factors which would favour the siting of an aluminium smelter in a country are the availability of cheap electricity and the presence of bauxite ore, which is the raw material used to produce aluminium.
(d)(i) Paramagnetism is the property of an atom, ion, or molecule that has unpaired electrons and is attracted by a magnetic field.
(ii) For 24Cr2+, there are 4 unpaired electrons, while for 24Cr6+, there are no unpaired electrons. Therefore, 24Cr2+ will have a greater power of paramagnetism.
Explanation for (d)(ii): The power of paramagnetism is directly proportional to the number of unpaired electrons. Since 24Cr2+ has 4 unpaired electrons, it will have a greater power of paramagnetism than 24Cr6+, which has no unpaired electrons. This is because the unpaired electrons in 24Cr2+ are available for alignment with an external magnetic field, whereas the paired electrons in 24Cr6+ are not.
(a)(i) The first ionization energy of an element is the amount of energy required to remove one electron from a neutral atom of that element in the gaseous state.
(ii) The missing value in the table is 730 kJ mol⁻¹ for the first ionization energy of lithium (Li).
Explanation for (a): The first ionization energy of B is less than that of Be because B has an electron in a p-orbital, which is further away from the nucleus than the s-orbital electrons in Be. As a result, the attraction between the nucleus and the outermost electron is weaker in B than in Be, making it easier to remove an electron from B.
(b) The amount of charge on the titanium ion can be calculated using the formula:
Charge = (Current x Time x IF) / Mass
where IF is the Faraday constant and equals 96500 C mol⁻¹.
Plugging in the values given, we get:
Charge = (0.12 A x 500 s x 96500 C mol⁻¹) / 0.015 g
Charge = 1.934 x 10⁶ C mol⁻¹
Since the charge on a single titanium ion is 4+, we can calculate the number of moles of titanium deposited by dividing the mass by the molar mass:
n(Ti) = 0.015 g / 48.0 g mol⁻¹ = 3.125 x 10⁻⁴ mol
Dividing the total charge by the number of moles of titanium gives us the charge on a single titanium ion:
Charge on Ti⁴⁺ ion = (1.934 x 10⁶ C mol⁻¹) / (3.125 x 10⁻⁴ mol) = 6.188 x 10⁹ C
(c)(i) The electrolyte which yields aluminium on electrolysis is molten cryolite (Na₃AlF₆) mixed with aluminium oxide (Al₂O₃).
(ii) Two major factors which would favour the siting of an aluminium smelter in a country are the availability of cheap electricity and the presence of bauxite ore, which is the raw material used to produce aluminium.
(d)(i) Paramagnetism is the property of an atom, ion, or molecule that has unpaired electrons and is attracted by a magnetic field.
(ii) For 24Cr2+, there are 4 unpaired electrons, while for 24Cr6+, there are no unpaired electrons. Therefore, 24Cr2+ will have a greater power of paramagnetism.
Explanation for (d)(ii): The power of paramagnetism is directly proportional to the number of unpaired electrons. Since 24Cr2+ has 4 unpaired electrons, it will have a greater power of paramagnetism than 24Cr6+, which has no unpaired electrons. This is because the unpaired electrons in 24Cr2+ are available for alignment with an external magnetic field, whereas the paired electrons in 24Cr6+ are not.
