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 2.1 Amount of chemical change Question Bank

[Maximum number: 2]

A student investigated how the type of acid in acid deposition affects limestone, a building material mainly composed of calcium carbonate.

The student monitored the mass of six similarly sized pieces of limestone. Three were placed in beakers containing $200.0 \mathrm{~cm}^{3}$ of $0.100 \mathrm{~mol} \mathrm{dm}^{-3}$ nitric acid, $\mathrm{HNO}_{3}(\mathrm{aq})$ , and the other three in $200.0 \mathrm{~cm}^{3}$ of $0.100 \mathrm{~mol} \mathrm{dm}^{-3}$ sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})$ .

The limestone was removed from the acid, washed, dried with a paper towel and weighed every day at the same time and then replaced in the beakers.

The student plotted the mass of one of the pieces of limestone placed in nitric acid against time.

(a)

(i)

Explain why the rate of reaction of limestone with nitric acid decreases and reaches zero over the period of five days.

[ 2 ]

[Maximum number: 1]

Combustion of ethanol takes place according to the following unbalanced equation.

{ }^{-} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l})+\ldots \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \ldots \mathrm{CO}_{2}(\mathrm{~g})+\ldots \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

What is the mole ratio of ethanol to oxygen in the balanced equation?

1: 1

2: 1

1: 3

2: 7

[Maximum number: 1]

What is the sum of the coefficients when the equation is balanced with the lowest whole number ratio?

\underline{\hspace{0.9em}} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq})+\underline{\hspace{0.9em}} \mathrm{HCl}(\mathrm{aq}) \rightarrow \underline{\hspace{1.8em}} \mathrm{S}(\mathrm{~s})+\underline{\hspace{0.9em}} \mathrm{SO}_{2}(\mathrm{~g})+\underline{\hspace{0.9em}} \mathrm{NaCl}(\mathrm{aq})+\underline{\hspace{0.9em}} \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

[Maximum number: 2]

Nitrogen dioxide, $\mathrm{NO}_{2}$ , is a brown, toxic and corrosive gas. It can be made in a school laboratory by heating a group II metal nitrate or by the reaction of copper, Cu , with concentrated nitric acid, $\mathrm{HNO}_{3}$ .

(a)

(i)

Deduce the coefficients in the equation for the reaction of Cu with concentrated $\mathrm{HNO}_{3}$ .

{ }_{-} \mathrm{Cu}(\mathrm{~s})+{ }_{-} \mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow{ }_{-} \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+{ }_{-} \mathrm{NO}_{2}(\mathrm{~g})+{ }_{-} \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

[ 1 ]

(ii)

Calculate the mass, in g , of Cu required to make 0.0100 moles of $\mathrm{NO}_{2}$ . Use section 7 of the data booklet.

[ 1 ]

[Maximum number: 1]

0.2 mol of sodium hydrogencarbonate is decomposed by heating until constant mass.

2 \mathrm{NaHCO}_{3}(\mathrm{~s}) \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g})+\mathrm{CO}_{2}(\mathrm{~g})

How many moles of gas are produced?

0.1

0.2

0.3

0.4

[Maximum number: 1]

How many moles of magnesium hydroxide are produced with 0.50 mol of ammonia?

\mathrm{Mg}_{3} \mathrm{~N}_{2}(\mathrm{~s})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow 3 \mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{aq})+2 \mathrm{NH}_{3}(\mathrm{aq})

0.25

0.33

0.75

1.5

[Maximum number: 1]

Ethanedioic acid is a diprotic acid. A student determined the value of x in the formula of hydrated ethanedioic acid, $\mathrm{HOOC}-\mathrm{COOH} \bullet \times \mathrm{H}_{2} \mathrm{O}$ , by titrating a known mass of the acid with a $0.100 \mathrm{~mol} \mathrm{dm}^{-3}$ solution of NaOH(aq).
0.795 g of ethanedioic acid was dissolved in distilled water and made up to a total volume of $250 \mathrm{~cm}^{3}$ in a volumetric flask.
$25 \mathrm{~cm}^{3}$ of this ethanedioic acid solution was pipetted into a flask and titrated against aqueous sodium hydroxide using phenolphthalein as an indicator.

The titration was then repeated twice to obtain the results below.

(a)

(i)

The equation for the reaction taking place in the titration is:

\mathrm{HOOC}-\mathrm{COOH}(\mathrm{aq})+2 \mathrm{NaOH}(\mathrm{aq}) \rightarrow \mathrm{NaOOC}-\mathrm{COONa}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

Determine the amount, in mol, of ethanedioic acid that reacts with the average volume of NaOH (aq).

[ 1 ]

[Maximum number: 3]

Chlorine undergoes many reactions.

(a)

2.67 g of manganese(IV) oxide was added to $200.0 \mathrm{~cm}^{3}$ of $2.00 \mathrm{moldm} \mathrm{m}^{-3} \mathrm{HCl}$ .

\mathrm{MnO}_{2}(\mathrm{~s})+4 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{MnCl}_{2}(\mathrm{aq})

[ 3 ]

(i)

Determine the limiting reactant, showing your calculations.

[ 2 ]

(ii)

Determine the excess amount, in mol , of the other reactant.

[ 1 ]

[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)

Calcium hydroxide reacts with carbon dioxide to reform calcium carbonate.

\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g}) \rightarrow \mathrm{CaCO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})

[ 1 ]

(i)

$2.85 \mathrm{~g}^{\circ} \mathrm{CaCO}_{3}$ was collected in the experiment in e(i). Calculate the percentage yield of $\mathrm{CaCO}_{3}$ .
(If you did not obtain an answer to e(i), use 4.00 g , but this is not the correct value.)

[ 1 ]

[Maximum number: 4]

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)

Determine the limiting reactant when 1.00 g of this powder reacts.

[ 3 ]

(ii)

Calculate the percentage yield obtained by a student who collected $0.043 \mathrm{dm}^{3}$ of carbon dioxide from 1.00 g of the powder.

If you did not obtain an answer to (a)(ii), use $0.068 \mathrm{dm}^{3}$ , but this is not the correct value.

[ 1 ]

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