Structure 1. Models of the particulate nature of matter

1.1 Introduction to the particulate nature of matter

1.2 The nuclear atom

1.3 Electron configurations

1.4 The mole

1.5 Ideal gases

Structure 2. Models of bonding and structure

2.1 The ionic model

2.2 The covalent model

2.3 The metallic model

2.4 From models to materials

Structure 3. Classification of matter

3.1 The periodic table

3.2 Functional groups: Organic compounds

Reactivity 1. What drives chemical reactions?

1.1 Measuring enthalpy changes

1.2 Energy cycles

1.3 Energy from fuels

Reactivity 2. How much, how fast and how far?

2.1 Amount of chemical change

2.2 Rate of chemical change

2.3 Extent of chemical change

Reactivity 3. What are the mechanisms of chemical change?

3.1 Proton transfer reactions

3.2 Electron transfer reactions

3.3 Electron sharing reactions (Radicals)

3.4 Electron-pair sharing reactions

IB Chemistry SL 3.1 Proton transfer reactions Question Bank

[Maximum number: 3]

Methanoic acid (HCOOH) is the first member of the homologous series of carboxylic acids.

(a)

Methanoic acid and ethanal $\left(\mathrm{CH}_{3} \mathrm{CHO}\right)$ both contain a carbonyl group and have similar molar masses.

[ 3 ]

(i)

Predict, giving an explanation, the relative electrical conductivity of solutions of methanoic acid, ethanal and hydrochloric acid of the same concentration.

Relative electrical conductivity: < <
Explanation:

[ 3 ]

[Maximum number: 4]

Hydrogen cyanide, HCN , is a very toxic compound.

(a)

HCN acts as a weak acid in aqueous solution.

[ 4 ]

(i)

Write an equation to show this behaviour.

[ 1 ]

(ii)

Outline two ways in which you could determine that a solution was $0.1 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCN}$ rather than $0.1 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}$ .

Method 1:
Method 2:

[ 2 ]

(iii)

Determine the pH of $0.100 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCN}(\mathrm{aq})$ if the $\left[\mathrm{H}^{+}\right]$ is $7.00 \times 10^{-6} \mathrm{moldm}^{-3}$ .

[ 1 ]

[Maximum number: 3]

Chlorine undergoes many reactions.

(a)

Chlorine gas reacts with water to produce hypochlorous acid and hydrochloric acid.

\mathrm{Cl}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightleftharpoons \mathrm{HClO}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq})

[ 3 ]

(i)

Hypochlorous acid is considered a weak acid. Outline what is meant by the term weak acid.

[ 1 ]

(ii)

State the formula of the conjugate base of hypochlorous acid.

[ 1 ]

(iii)

Calculate the concentration of $\mathrm{H}^{+}(\mathrm{aq})$ in a HClO(aq) solution with a pH=3.61.

[ 1 ]

[Maximum number: 4]

A student used a pH meter to measure the pH of different samples of water at 298 K .

(a)

Use the data in the table to identify the most acidic water sample.

[ 1 ]

(b)

Determine the ratio of $\left[\mathrm{H}^{+}\right]$ in bottled water to that in rain water.

[ 2 ]

(c)

The acidity of non-polluted rain water is caused by dissolved carbon dioxide. State an equation for the reaction of carbon dioxide with water.

[ 1 ]

[Maximum number: 3]

A powder has the following percentage composition by mass:
30.0 % sucrose, $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$
45.0 % citric acid, $\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}$
25.0 \% sodium hydrogencarbonate, $\mathrm{NaHCO}_{3}$

In the presence of water, the powder effervesces as the citric acid reacts with the sodium hydrogencarbonate:

$3 \mathrm{NaHCO}_{3}(\mathrm{~s})+\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}(\mathrm{aq}) \rightarrow \mathrm{Na}_{3}\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right)(\mathrm{aq})+3 \mathrm{CO}_{2}(\mathrm{~g})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})$

(a)

(i)

Deduce the structural formula of the conjugate base of citric acid.

[ 1 ]

(ii)

Predict, giving a reason, the strength of citric acid.

[ 1 ]

(b)

Calculate the pH of a solution with a hydrogen ion concentration,
$\left[\mathrm{H}^{+}\right]=0.0025 \mathrm{~mol} \mathrm{dm}^{-3}$ .

[ 1 ]

[Maximum number: 3]

A student decided to determine the molecular mass of a solid monoprotic acid, HA, by titrating a solution of a known mass of the acid.

The following recordings were made.

(a)

A solution of HA is a weak acid. Distinguish between a weak acid and a strong acid.

[ 1 ]

(b)

Describe an experiment, other than measuring the pH , to distinguish HA from a strong acid of the same concentration and describe what would be observed.

[ 2 ]

[Maximum number: 1]

Limestone can be converted into a variety of useful commercial products through the lime cycle. Limestone contains high percentages of calcium carbonate, $\mathrm{CaCO}_{3}$ .

(a)

The second step of the lime cycle produces calcium hydroxide, $\mathrm{Ca}(\mathrm{OH})_{2}$ .

[ 1 ]

(i)

Write the equation for the reaction of $\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})$ with hydrochloric acid, HCl(aq).

[ 1 ]

[Maximum number: 2]

When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.

(a)

The presence of magnesium nitride can be demonstrated by adding water to the product. It is hydrolysed to form magnesium hydroxide and ammonia.

[ 2 ]

(i)

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid-base reaction, a redox reaction, neither or both.

Acid-base: Yes No

Reason:

Redox: Yes No

Reason:

[ 2 ]

[Maximum number: 1]

A student determined the percentage of the active ingredient magnesium hydroxide, $\mathrm{Mg}(\mathrm{OH})_{2}$ , in a 1.24 g antacid tablet.

The antacid tablet was added to $50.00 \mathrm{~cm}^{3}$ of $0.100 \mathrm{~mol} \mathrm{dm}^{-3}$ sulfuric acid, which was in excess.

(a)

Formulate the equation for the reaction of $\mathrm{H}_{2} \mathrm{SO}_{4}$ with $\mathrm{Mg}(\mathrm{OH})_{2}$ .

[ 1 ]

[Maximum number: 2]

Ammonium nitrate, $\mathrm{NH}_{4} \mathrm{NO}_{3}$ , is used as a high nitrogen fertilizer.

(a)

State, with a reason, whether the ammonium ion is a Brønsted-Lowry acid or base.

[ 1 ]

(b)

Calculate the pH of an ammonium nitrate solution with
$\left[\mathrm{H}_{3} \mathrm{O}^{+}\right]=1.07 \times 10^{-5} \mathrm{~mol} \mathrm{dm}{ }^{-3}$ . Use section 1 of the data booklet.

[ 1 ]

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