ASChemistryCIEExam Questions7. Equilibria7.2 Brønsted–Lowry Theory of Acids & Bases

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First exams 2025

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Brønsted–Lowry Theory of Acids & Bases (CIE AS Chemistry)

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7.2 Brønsted–Lowry Theory of Acids & Bases

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7.2 Brønsted–Lowry Theory of Acids & Bases

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1
Sme Calculator1 mark

Which type of titration is indicated by the following pH curve?

PH curve

  • Strong acid - strong base

  • Weak acid - weak base

  • Strong acid - weak base

  • Weak acid - strong base

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21 mark

Using your knowledge of the Brønsted-Lowry theory, which of the following correctly describes ammonia?

  • neutral

  • acid

  • base

  • amphoteric

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31 mark

In the following reaction, identify which two species are acting as Brønsted–Lowry acids

H3PO4 (aq) + OH− (aq)  ⇋ H2PO4− (aq) + H2O (l)

  • H2PO4− (aq) and OH− (aq)

  • H3PO4 (aq) and H2PO4− (aq)

  • H2PO4− (aq) and H2O (l)

  • H3PO4 (aq) and H2O (l)

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11 mark

The table gives the concentrations and pH values of the aqueous solutions of two compounds, P and Q. Either compound could be an acid or a base.

 

P

Q

Concentration

pH

2 mol dm–3

9

2 mol dm–3

6

Student X concluded that Q is a strong acid. 

Student Y concluded that the extent of dissociation is lower in Q (aq) than in P (aq). 

Which of the students are correct?

  • X only

  • Y only

  • Both X and Y

  • Neither X nor Y

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21 mark

The pH range of four different indicators are:

Indicator pH range for colour change
Methyl orange 3.2 - 4.4 
Phenolphthalein 8.2 - 10.0
Thymol blue 1.2 - 2.8 
Bromothymol blue  6.0 - 7.6 


Which indicator would be suitable for a titration involving hydrochloric acid and ammonia?

  • Methyl orange

  • Phenolphthalein

  • Thymol blue

  • Bromothymol blue

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31 mark

The following reaction occurs between concentrated sulfuric and nitric acids.

H2SO4 + HNO3 ⇋  H2NO3+ + HSO4-

Identify the two species which are acting as Brønsted–Lowry bases.

  • H2NO3+ and HSO4-

  • HNO3 and H2NO3+

  • H2SO4 and HSO4- 

  • HNO3 and HSO4-

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11 mark

The following equilibrium is set up in a mixture of sulfuric acid and concentrated nitric acid.

H2SO4 + HNO3   ⇌   HSO4- + H2NO3+ 

Which row correctly describes the behaviour of each molecule within the equilibrium?

 

H2SO4

HNO3

HSO4–

H2NO3+

A

B

C

D

Acid

Base

Acid

Acid

Acid

Acid

Base

Base

Base

Acid

Base

Acid

Base

Base

Acid

Base

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    21 mark

    Which species are Bronsted-Lowry acids in the reaction shown?

    H2PO4− (aq) + CN- (aq) ⇌  HCN (aq)  + HPO42− (aq)

    • HCN and H2PO4−

    • HCN and CN-

    • H2PO4− and HPO42−

    • HCN and HPO42−

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    31 mark

    Which of the following statements is incorrect about  0.01 mol dm–3 CH3COOH?

    • the pH = 2

    • [H+] << 0.01 mol dm–3

    • [CH3COO–] is approximately equal to [H+]

    • CH3COOH is partially ionized

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