The formula of an aluminium ion is Al$^{3+}$ - Edexcel - GCSE Chemistry - Question 2 - 2017 - Paper 1
Question 2
The formula of an aluminium ion is Al$^{3+}$.
The formula of a sulfate ion is SO$_{4}^{2-}$.
(i) Which of the following is the correct formula of aluminium sulf... show full transcript
Worked Solution & Example Answer:The formula of an aluminium ion is Al$^{3+}$ - Edexcel - GCSE Chemistry - Question 2 - 2017 - Paper 1
Step 1
Which of the following is the correct formula of aluminium sulfate?
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Answer
The formula of aluminium sulfate is Al(SO4)3. This represents that for every 1 aluminium ion, three sulfate ions are required to balance the charges, as aluminium has a +3 charge and sulfate has a -2 charge.
Step 2
To test for the presence of sulfate ions in a solid, the solid is first dissolved in water and then two solutions are added.
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Answer
To test for sulfate ions, you can add barium chloride solution and hydrochloric acid. Barium chloride reacts with sulfate ions to produce barium sulfate, which forms a white precipitate.
Step 3
Which of these substances is insoluble in water?
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Answer
Lead sulfate (option C) is insoluble in water. It is one of the common insoluble sulfates due to the low solubility of lead ions in water.
Step 4
Describe, in terms of their electronic configurations, how calcium and oxygen atoms react to form calcium and oxide ions.
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Calcium has an electronic configuration of 2.8.8 and loses 2 electrons to achieve a stable noble gas configuration, forming a Ca2+ ion (2.8). Oxygen has an electronic configuration of 2.6 and gains 2 electrons to become O2− (2.8). Therefore, calcium forms Ca2+ ions and oxygen forms O2− ions, resulting in the formation of calcium oxide (CaO). Diagrams can illustrate the transfer of electrons from calcium to oxygen.
