May/June 2026 Paper 43

2026 · 9 questions · 63 parts · 100 marks

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

–/14 mks

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

–/11 mks

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

–/9 mks

4(a)4(b)4(c)4(d)4(e)

–/10 mks

5(a)5(b)5(c)5(d)5(e)(i)5(e)(ii)5(e)(iii)5(e)(iv)

–/13 mks

6(a)6(b)(i)6(b)(ii)6(b)(iii)6(c)

–/8 mks

7(a)(i)7(a)(ii)7(a)(iii)7(b)(i)7(b)(ii)7(b)(iii)7(b)(iv)7(b)(v)7(c)(i)7(c)(ii)

–/14 mks

8(a)(i)8(a)(ii)8(a)(iii)8(a)(iv)8(a)(v)8(a)(vi)8(b)(i)8(b)(ii)

–/10 mks

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

–/11 mks

2(a)(i)Ph Ionic Product WaterEasy1 mark

Define pH mathematically.

2(a)(ii)Ph Ionic Product WaterEasy1 mark

Define

K_{w}

mathematically.

Answer

0 words

2(b)(i)Weak Acids Bases BuffersEasy1 mark

Solution A is 100 cm

^{3}

of an aqueous solution of 0.105 mol dm

^{- 3}

butanoic acid, CH

_{3}

_{2}

_{2}

COOH. A has pH 2.90 at 298 K.

Calculate the concentration, in mol dm

^{- 3}

, of H

^{+}

(aq) in A.

^{+}

] in A

2(b)(ii)Weak Acids Bases BuffersMedium1 mark

Calculate the value of

K_{a}

of CH

_{3}

_{2}

_{2}

COOH at 298 K.

K_{a}

of CH

_{3}

_{2}

_{2}

COOH

2(c)(i)Weak Acids Bases BuffersHard3 marks

Solution B is 100 cm

^{3}

of an aqueous solution containing 0.450 mol dm

^{- 3}

_{3}

_{2}

_{2}

COOH. Solution C is 200 cm

^{3}

of an aqueous solution containing sodium butanoate, CH

_{3}

_{2}

_{2}

COONa.

B is added to C to produce 300 cm

^{3}

of solution D. The concentration of H

^{+}

ions in D is

6.31 \times 1 0^{- 5}

mol dm

^{- 3}

Calculate the concentration of CH

_{3}

_{2}

_{2}

COONa in C. (If you were unable to calculate an answer in part (b)(ii), use

3.00 \times 1 0^{- 5}

as the value of

K_{a}

of CH

_{3}

_{2}

_{2}

COOH. This is not the correct answer.)

[CH

_{3}

_{2}

_{2}

COONa] in C

0 words

2(c)(ii)Weak Acids Bases BuffersMedium1 mark

Write an equation for the reaction when H

_{2}

_{4}

(aq) is added to D.

Answer

0 words

2(c)(iii)Weak Acids Bases BuffersMedium1 mark

Write an equation for the reaction when KOH(aq) is added to D.

Answer

0 words

2(d)Carboxylic Acids EstersMedium2 marks

Predict the relative acidities of 2,2-dichlorobutanoic acid, CH

_{3}

_{2}

CCl

_{2}

COOH, and butanoic acid, CH

_{3}

_{2}

_{2}

COOH. Explain your answer.

Answer

0 words