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Context for question 3

A student tests two substances: solution A and solid B.

Tests on solution A

Table 3.1 shows the tests and the student’s observations for solution A.

Table 3.1

tests	observations
Divide solution A into three portions. test 1 To the first portion of solution A, add sodium hydroxide dropwise and then in excess.	white precipitate precipitate remains in excess
test 2 To the second portion of solution A, add 1 cm $^{3}$ of dilute nitric acid and a few drops of aqueous silver nitrate.	white precipitate
test 3 To the third portion of solution A, add an equal depth of dilute sulfuric acid and leave to stand for 5 minutes. Keep the contents of the test-tube for use in test 4.	white precipitate
test 4 Add an equal depth of aqueous sodium carbonate to the contents of the test-tube from test 3. Any gas given off is tested.	effervescence gas turns limewater milky

Notes for use in qualitative analysis

Tests for anions

anion	test	test result
carbonate, CO $_{3}^{2 -}$	add dilute acid, then test for carbon dioxide gas	effervescence, carbon dioxide produced
chloride, Cl $^{-}$ [in solution]	acidify with dilute nitric acid, then add aqueous silver nitrate	white ppt.
bromide, Br $^{-}$ [in solution]	acidify with dilute nitric acid, then add aqueous silver nitrate	cream ppt.
iodide, I $^{-}$ [in solution]	acidify with dilute nitric acid, then add aqueous silver nitrate	yellow ppt.
nitrate, NO $_{3}^{-}$ [in solution]	add aqueous sodium hydroxide, then aluminium foil; warm carefully	ammonia produced
sulfate, SO $_{4}^{2 -}$ [in solution]	acidify with dilute nitric acid, then add aqueous barium nitrate	white ppt.
sulfite, SO $_{3}^{2 -}$	add a small volume of acidified aqueous potassium manganate(VII)	the acidified aqueous potassium manganate(VII) changes colour from purple to colourless

Tests for aqueous cations

cation	effect of aqueous sodium hydroxide	effect of aqueous ammonia
aluminium, Al $^{3 +}$	white ppt., soluble in excess, giving a colourless solution	white ppt., insoluble in excess
ammonium, NH $_{4}^{+}$	ammonia produced on warming	–
calcium, Ca $^{2 +}$	white ppt., insoluble in excess	no ppt. or very slight white ppt.
chromium(III), Cr $^{3 +}$	green ppt., soluble in excess	green ppt., insoluble in excess
copper(II), Cu $^{2 +}$	light blue ppt., insoluble in excess	light blue ppt., soluble in excess, giving a dark blue solution
iron(II), Fe $^{2 +}$	green ppt., insoluble in excess, ppt. turns brown near surface on standing	green ppt., insoluble in excess, ppt. turns brown near surface on standing
iron(III), Fe $^{3 +}$	red-brown ppt., insoluble in excess	red-brown ppt., insoluble in excess
zinc, Zn $^{2 +}$	white ppt., soluble in excess, giving a colourless solution	white ppt., soluble in excess, giving a colourless solution

Tests for gases

gas	test and test result
ammonia, NH $_{3}$	turns damp red litmus paper blue
carbon dioxide, CO $_{2}$	turns limewater milky
chlorine, Cl $_{2}$	bleaches damp litmus paper
hydrogen, H $_{2}$	‘pops’ with a lighted splint
oxygen, O $_{2}$	relights a glowing splint
sulfur dioxide, SO $_{2}$	turns acidified aqueous potassium manganate(VII) from purple to colourless

Flame tests for metal ions

metal ion	flame colour
lithium, Li $^{+}$	red
sodium, Na $^{+}$	yellow
potassium, K $^{+}$	lilac
calcium, Ca $^{2 +}$	orange-red
barium, Ba $^{2 +}$	light green
copper(II), Cu $^{2 +}$	blue-green

3(a)Easy1 mark

State what conclusion can be made about solution A from the observations in test 1.

3(b)Easy1 mark

State what conclusion can be made about solution A from the observations in test 2.

3(c)Easy2 marks

A flame test is used to confirm the identity of the cation in solution A. Describe how to carry out a flame test.

Your answer

3(d)Easy1 mark

Suggest what the sodium carbonate reacts with in test 4 to produce carbon dioxide gas.

Your answer

Context for 3(e)

Tests on solid B

Solid B is zinc sulfate. The student dissolves solid B in water to form solution B. The student divides solution B into three approximately equal portions into one boiling tube and two test-tubes. Complete the expected observations.

3(e)Easy2 marks

To the first portion of solution B in the boiling tube, the student adds aqueous sodium hydroxide dropwise and then in excess.

observations

3(f)Easy1 mark

To the second portion of solution B in a test-tube, the student adds 1 cm

^{3}

of dilute nitric acid followed by a few drops of aqueous barium nitrate.

observations

3(g)Easy1 mark

To the third portion of solution B in a test-tube, the student adds 1 cm

^{3}

of dilute nitric acid followed by a few drops of aqueous silver nitrate.

observations

May/June 2026 Paper 63

Questions

Tests on solution A

Notes for use in qualitative analysis

Tests on solid B