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Context for question 3

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

Tests on solid A

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

Table 3.1

tests	observations
test 1 Place about half of solid A in a boiling tube. Heat solid A strongly in the boiling tube.	solid A turns black
test 2 Place the remaining solid A in a boiling tube. Add 10 cm $^{3}$ of dilute hydrochloric acid to the boiling tube. Test any gas given off. The solution that forms is solution C.	effervescence is seen some of solid A dissolves to form a blue solution limewater turns milky
test 3 Solution C is divided into three approximately equal portions. To the first portion of solution C, add aqueous sodium hydroxide dropwise and then in excess.	blue precipitate forms which remains in excess
test 4 To the second portion of solution C, add 1 cm $^{3}$ of dilute nitric acid followed by a few drops of aqueous barium nitrate.	no visible change

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

Identify the gas given off in test 2.

3(b)Easy1 mark

State the conclusion about solid A that can be made from the observation in test 4.

3(c)Medium2 marks

Identify solid A.

cation in solid A

anion in solid A

3(d)Easy2 marks

To the third portion of solution C, the student adds excess aqueous ammonia.

Observations

3(e)

Tests on solution B

Solution B is aqueous barium chloride.

The student divides solution B into three equal portions.

Record the expected observations.

The student carries out a flame test on the first portion of solution B.

3(e)(i)Easy1 mark

State the type of Bunsen burner flame the student should use when carrying out a flame test.

3(e)(ii)Easy1 mark

State the result of the flame test on solution B.

3(f)Easy1 mark

To the second portion of solution B, the student adds about 1 cm

^{3}

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

Observations

3(g)Easy1 mark

To the third portion of solution B, the student adds about 1 cm

^{3}

of dilute sulfuric acid.

Observations

February/March 2026 Paper 62

Questions

Tests on solid A

Notes for use in qualitative analysis

Tests on solution B