May/June 2026 Paper 42

2026 · 9 questions · 56 parts · 100 marks

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1(a)(i)1(a)(ii)1(b)(i)1(b)(ii)1(c)1(d)(i)1(d)(ii)1(e)1(f)(i)1(f)(ii)1(g)1(h)

–/20 mks

2(a)2(b)2(c)2(d)(i)2(d)(ii)2(d)(iii)

–/10 mks

3(a)(i)3(a)(ii)3(a)(iii)3(b)3(c)

–/10 mks

4(a)4(b)4(c)

–/6 mks

5(a)5(b)(i)5(b)(ii)5(b)(iii)5(c)

–/11 mks

6(a)(i)6(a)(ii)6(b)6(c)(i)6(c)(ii)6(d)6(e)(i)6(e)(ii)

–/14 mks

7(a)(i)7(a)(ii)7(b)(i)7(b)(ii)7(c)7(d)(i)7(d)(ii)

–/11 mks

8(a)8(b)(i)8(b)(ii)8(b)(iii)8(c)

–/8 mks

9(a)9(b)(i)9(b)(ii)9(c)(i)9(c)(ii)

–/10 mks

1(a)(i)Transition Metals Their ReactionsEasy1 mark

Transition elements have variable oxidation states and form complex ions.

State two other typical chemical properties of a transition element.

Two answers required.

1(a)(ii)Transition Metals Their ReactionsEasy1 mark

Explain why transition elements have variable oxidation states.

Answer

0 words

1(b)(i)Electron Configuration OrbitalsEasy1 mark

An aqueous solution of chromium(III) ions, Cr

^{3 +}

, contains the [Cr(H

_{2}

_{6}

]

^{3 +}

complex ion.

Complete Figure 1.1 to show the electronic configuration for Cr

^{3 +}

Draw with the mouse or a finger.

1(b)(ii)Complex Ions Colour Ligand ExchangeEasy1 mark

State the type of bonding that exists between H

_{2}

O and Cr

^{3 +}

in [Cr(H

_{2}

_{6}

]

^{3 +}

1(c)Complex Ions Colour Ligand ExchangeEasy1 mark

Explain why transition elements form complex ions.

Answer

0 words

1(d)(i)Transition Metals Their ReactionsEasy1 mark

[Cr(H

_{2}

_{6}

]

^{3 +}

can be converted into the [Cr(H

_{2}

_{3}

(OH)

_{3}

] complex. Suggest a suitable reagent for this conversion, and state the type of reaction.

1(d)(ii)Complex Ions Colour Ligand ExchangeMedium2 marks

[Cr(H

_{2}

_{3}

(OH)

_{3}

] reacts with an excess of NH

_{3}

(aq) to form [Cr(NH

_{3}

)

_{6}

]

^{3 +}

. Complete the equation for this reaction, and state the type of reaction.

Equation

0 words

Type of reaction

1(e)Complex Ions Colour Ligand ExchangeMedium2 marks

[Cr(H

_{2}

_{3}

(OH)

_{3}

] shows stereoisomerism.

Draw three-dimensional diagrams in Figure 1.2 to suggest the two stereoisomers of [Cr(H

_{2}

_{3}

(OH)

_{3}

Draw with the mouse or a finger.

1(f)(i)Transition Metals Their ReactionsMedium2 marks

An aqueous solution of iron(III) ions, Fe

^{3 +}

, contains the [Fe(H

_{2}

_{6}

]

^{3 +}

complex ion. This solution is acidic in a similar way to an aqueous solution of Al

^{3 +}

. Suggest why a solution of Fe

^{3 +}

is acidic. Include an equation in your answer.

Explanation

0 words

Equation

0 words

1(f)(ii)Transition Metals Their ReactionsMedium1 mark

An aqueous solution of iron(II) ions, Fe

^{2 +}

, contains the [Fe(H

_{2}

_{6}

]

^{2 +}

complex ion. This solution is also acidic. Predict how the pH of 1.00 mol dm

^{- 3}

^{2 +}

(aq) differs from the pH of 1.00 mol dm

^{- 3}

^{3 +}

(aq). Explain your answer.

Answer

0 words

1(g)Complex Ions Colour Ligand ExchangeMedium2 marks

Suggest why solutions of silver(I) salts are colourless.

Answer

0 words

1(h)Concentration Solutions Titration CalculationsHard5 marks

A mixture contains sodium ethanedioate, Na

_{2}

_{2}

_{4}

, ethanedioic acid dihydrate, H

_{2}

_{2}

_{4}

• 2H

_{2}

O, and an unreactive solid. 5.00 g of this mixture is dissolved in distilled water and made up to 500 cm

^{3}

in a volumetric flask to form solution A. Two different titration experiments are carried out using A. In the first experiment, 25.0 cm

^{3}

of A requires 21.80 cm

^{3}

of acidified 0.0250 mol dm

^{- 3}

MnO

_{4}^{-}

(aq) to reach the end-point.

2 M n O_{4}^{-} + 5 C_{2} O_{4}^{2 -} + 16 H^{+} \to 2 M n^{2 +} + 10 C O_{2} + 8 H_{2} O

In the second experiment, 25.0 cm

^{3}

of A requires 13.60 cm

^{3}

of 0.150 mol dm

^{- 3}

^{-}

(aq) to reach the end-point.

H_{2} C_{2} O_{4} + 2 O H^{-} \to C_{2} O_{4}^{2 -} + 2 H_{2} O

Calculate the percentage by mass of Na

_{2}

_{2}

_{4}

in the mixture. [

M_{r}

: Na

_{2}

_{2}

_{4}

, 134.0]

Draw with the mouse or a finger.