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Question 25

A student carried out a series of tests on a solid, Y, in order to identify the ions that could be present. Her results are as follows:

  • Test 1: A flame test on solid Y produced a lilac flame.
  • Test 2: Solid Y was dissolved in water, and the solution was divided into three portions, A, B, and C.
    • For Portion A, adding dilute sodium hydroxide solution produced a green precipitate.
    • For Portion B, adding dilute nitric acid followed by silver nitrate solution produced a cream precipitate.
    • For Portion C, adding dilute hydrochloric acid followed by barium chloride solution resulted in no change.
a.

Identify the ion responsible for: (i) the lilac colour in the flame test; (ii) the green precipitate when sodium hydroxide solution was added; (iii) the cream precipitate when silver nitrate solution was added.

[3]
b.

Describe how the student should carry out a flame test on solid Y.

[3]
c.

(i) Why was dilute nitric acid added to the solution of solid Y before using silver nitrate solution? (ii) Why should dilute hydrochloric acid not be used in place of dilute nitric acid in this test?

[3]
d.

Suggest one negative ion that cannot be identified by a presidency reaction.

[1]

Chemical tests Questions

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