CAIE IGCSE Chemistry 7.1 The characteristic properties of acids & bases Question Bank

Practise characteristic acid and base behaviour using indicators, pH data, H+ ions, alkalis, neutralisation and reaction equations.

Exam points

use pH data to compare H+ concentration and identify the most acidic solution
write or complete neutralisation equations, including H+ + OH- -> H2O

Covered syllabus points

7.1.1—Characteristic properties of acids in 7.1.2—Acids in terms of their effect on: (a)7.1.3—Bases are oxides or hydroxides of 7.1.4—Characteristic properties of bases in 7.1.5—Alkalis in terms of their effect on 7.1.6—Aqueous solutions of acids contain H+7.1.7—To compare hydrogen ion concentration 7.1.8—Neutralisation reaction between an 7.1.9—Acids as proton donors and bases as 7.1.10—Strong acid as an acid that is 7.1.11—Hydrochloric acid is a strong acid, as 7.1.12—Ethanoic acid is a weak acid, as shown

[Maximum number: 5]

Sulfuric acid can be manufactured from the raw materials sulfur, air and water. The process can be divided into four stages.
stage 1 converting sulfur into sulfur dioxide
stage 2 converting sulfur dioxide into sulfur trioxide
stage 3 converting sulfur trioxide into oleum, $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$
stage 4 converting oleum into sulfuric acid
stage 1

(a)

Sulfuric acid reacts with a hydrocarbon called benzene to produce benzenesulfonic acid, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3} \mathrm{H}$ . Benzenesulfonic acid is a strong acid which ionises to produce hydrogen ions, $\mathrm{H}^{+}$ , and benzenesulfonate ions, $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3}{ }^{-}$ .

[ 5 ]

(i)

What is meant by the term strong acid?

[ 1 ]

(ii)

Describe how to show that a $1 \mathrm{~mol} / \mathrm{dm}^{3}$ solution of benzenesulfonic acid is a strong acid.

[ 2 ]

(iii)

Write a chemical equation for the reaction between benzenesulfonic acid and sodium carbonate, $\mathrm{Na}_{2} \mathrm{CO}_{3}$ .

[ 2 ]

$\mathrm{Na}_{2} \mathrm{CO}_{3}+2 \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3} \mathrm{H} \rightarrow 2 \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3} \mathrm{Na}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$

formula of $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{SO}_{3} \mathrm{Na}$ all formulae correct and balancing correct

[Maximum number: 2]

Dilute hydrochloric acid reacts with sodium carbonate solution.

2 \mathrm{HCl}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \rightarrow 2 \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g})

$2\mathrm{HCl(aq)}+\mathrm{Na_2CO_3(aq)} ightarrow2\mathrm{NaCl(aq)}+\mathrm{H_2O(l)}+\mathrm{CO_2(g)}$

(a)

Explain why effervescence is seen during the reaction.

[ 1 ]

(b)

Dilute hydrochloric acid was titrated with sodium carbonate solution.
- $10.0 \mathrm{~cm}^{3}$ of $0.100 \mathrm{~mol} / \mathrm{dm}^{3}$ hydrochloric acid were placed in a conical flask.
- A few drops of methyl orange indicator were added to the dilute hydrochloric acid.
- The mixture was titrated with sodium carbonate solution.
- $16.2 \mathrm{~cm}^{3}$ of sodium carbonate solution were required to react completely with the acid.

[ 1 ]

(i)

What colour would the methyl orange indicator be in the hydrochloric acid?

[ 1 ]

[Maximum number: 11]

Solid sodium hydroxide is a base which dissolves to form an aqueous solution, NaOH(aq).

(a)

State what is meant by the term base.

[ 1 ]

(b)

State the term given to a base which dissolves to form an aqueous solution.

[ 1 ]

(c)

State the colour of thymolphthalein in NaOH(aq).

[ 1 ]

(d)

Complete the word equation for the reaction of NaOH(aq) with ammonium chloride.

Figure for Question (d) — CAIE IGCSE Chemistry

[ 3 ]

(e)

Ethanoic acid, $\mathrm{CH}_{3} \mathrm{COOH}$ , is a weak acid.

[ 5 ]

(i)

Suggest the pH of dilute ethanoic acid.

[ 1 ]

$3 \leq \mathrm{pH}<7$

(ii)

Complete the symbol equation to show the dissociation of ethanoic acid.
$\mathrm{CH}_{3} \mathrm{COOH}$

[ 3 ]

i

$\mathrm{CH}_{3} \mathrm{COOH} \rightleftharpoons \mathrm{CH}_{3} \mathrm{COO}^{-}+\mathrm{H}^{+}$

M1 $\mathrm{H}^{+}$

M2 $\mathrm{CH}_{3} \mathrm{COO}^{-}$

M3 use of ⇌

(iii)

Write the ionic equation for the reaction when an acid neutralises a soluble base.

[ 1 ]

$\mathrm{H}^{+}+\mathrm{OH}^{-} \rightarrow \mathrm{H}_{2} \mathrm{O}$

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Covered syllabus points

7.1 The characteristic properties of acids and bases question 1

Question (a)

Question (i)

Question (ii)

Question (iii)

7.1 The characteristic properties of acids and bases question 2

Question (a)

Question (b)

Question (i)

7.1 The characteristic properties of acids and bases question 3

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)

Question (i)

Question (ii)

Question (iii)