Section 1: Rates, atoms and bonding

Read a rate from the graph or table as change divided by time, with its unit. Name the bonding before you explain a property.

A lesson for this section

Multiple choice, Section 1 style

Question 1

Volume of hydrogen collected at each time.
Time / s	Volume of hydrogen / cm³
0	0
20	48
40	78
60	90
80	90

A pupil adds magnesium ribbon to dilute hydrochloric acid and collects the hydrogen in a gas syringe. The table shows the results. What is the average rate of the reaction between 20 s and 40 s?

Question 2

Marble chips are added to dilute hydrochloric acid in a flask on a balance. In the first 60 s the reading falls from 152.40 g to 151.20 g as carbon dioxide escapes. What is the average rate of the reaction over the first 60 s?

Question 3

Magnesium reacts with dilute hydrochloric acid, the acid in excess. Why does the rate of the reaction fall as the reaction goes on?

Question 4

The graph shows the volume of gas given off as zinc reacts with an excess of dilute sulfuric acid. At what time did the reaction stop?

Question 5

Calcium carbonate powder reacts faster with dilute hydrochloric acid than the same mass of calcium carbonate lumps. Why?

Question 6

Which statement about a catalyst is correct?

Question 7

0.24 g of magnesium reacts with an excess of dilute hydrochloric acid and gives 240 cm³ of hydrogen. The experiment is repeated with 0.12 g of magnesium and the same volume and concentration of acid. What final volume of hydrogen is made?

Question 8

A pupil investigates how temperature affects the rate of the reaction between sodium thiosulfate solution and dilute hydrochloric acid. A cloudy yellow solid of sulfur forms, and the pupil times how long it takes for a cross under the flask to disappear. What must the pupil keep the same to make it a fair test?

Question 9

Marble chips react with dilute hydrochloric acid in a conical flask on a balance. A loose plug of cotton wool is placed in the neck of the flask. What is the plug for?

Question 10

Which method could a pupil use to measure the volume of hydrogen given off when magnesium reacts with dilute acid?

Question 11

How many protons, neutrons and electrons are in the selenide ion ⁸⁰₃₄Se²⁻?

Question 12

Protons and neutrons in four atoms.
Atom	Protons	Neutrons
W	17	18
X	20	20
Y	17	20
Z	19	21

The table shows the numbers of protons and neutrons in four atoms, W, X, Y and Z. Which two atoms are isotopes of the same element?

Question 13

An atom has the electron arrangement 2,8,6. Which element is it?

Question 14

An element has the electron arrangement 2,8,8,2. Which statement about the element is correct?

Question 15

In what order are the elements arranged in the periodic table?

Question 16

Which describes a neutron?

Question 17

In a molecule of hydrogen sulfide, H₂S, the sulfur atom forms two covalent bonds, just as oxygen does in water. What is the shape of the molecule?

Question 18

Which element exists as diatomic molecules?

Question 19

What holds the atoms together in a covalent bond?

Question 20

Which describes the bonding in a nitrogen molecule, N₂?

Question 21

Substance X melts at over 1600 °C, does not dissolve in water and does not conduct electricity, either as a solid or when molten. What type of structure does X have?

Question 22

Methane boils at −162 °C. Why is its boiling point so low?

Question 23

Why do covalent molecular substances not conduct electricity?

Question 24

Which ion-electron equation shows a sulfur atom forming a sulfide ion?

Question 25

Which ion has the same electron arrangement as an atom of neon?

Question 26

Why does solid sodium chloride not conduct electricity?

Question 27

What is an ionic bond?

Question 28

Molten zinc chloride, ZnCl₂, conducts electricity. Which describes what happens in the molten compound?

Question 29

A pupil uses a circuit with a bulb and two carbon electrodes to test a white solid, first as dry crystals and then dissolved in water. Which results show that the solid is ionic?

Question 30

What happens to the structure of potassium chloride when it dissolves in water?

Question 31

Volume of hydrogen in the syringe each minute.
Time / min	Volume of hydrogen / cm³
0	0
1	54
2	84
3	102
4	108
5	108

A pupil follows the reaction of zinc with dilute hydrochloric acid by reading the volume of hydrogen in a gas syringe once a minute. The table shows the results. What is the average rate of the reaction between 1 minute and 3 minutes, in cm³ s⁻¹?

Question 32

Excess marble chips react with 50 cm³ of 1.0 mol l⁻¹ hydrochloric acid, and the volume of carbon dioxide is measured until the reaction stops. The experiment is repeated at the same temperature with the same mass of marble chips, still in excess and fully covered, but with 100 cm³ of 0.50 mol l⁻¹ hydrochloric acid. Compared with the first, how does the graph for the second experiment look?

Question 33

Which pair of particles has the same number of electrons and also the same number of neutrons?

Question 34

An ion of element Q, Q³⁺, has the electron arrangement 2,8. Which statement about element Q is correct?

Question 35

Element X has the electron arrangement 2,6 and element Y has the electron arrangement 2,7. X and Y form a covalent molecular compound. Which gives the formula of a molecule of the compound and its shape?

Question 36

Data for four substances.
Substance	Melting point / °C	Boiling point / °C	Conducts as a solid	Conducts as a liquid
W	−95	111	no	no
X	44	280	no	no
Y	−39	357	yes	yes
Z	1710	2230	no	no

The table gives data for four substances, W, X, Y and Z. Which substance is covalent molecular and a liquid at 25 °C?

Question 37

In which compound do the positive ions and the negative ions have the same electron arrangement?

Question 38

Lithium burns in nitrogen, N₂, to form lithium nitride, an ionic compound that contains nitride ions. Which ion-electron equation shows nitrogen molecules forming nitride ions?

Question 39

0.50 g of manganese dioxide is added to hydrogen peroxide solution, which quickly gives off oxygen. When the reaction is over, the manganese dioxide is filtered off, washed and dried. What mass of manganese dioxide would you expect to recover?

Question 40

An atom has a mass number of 31 and contains 16 neutrons. Which element is it?

Section 2 questions, then experiment questions

Decomposing hydrogen peroxideSection 2 question · 8 marks

Hydrogen peroxide solution decomposes slowly on its own, but quickly when manganese dioxide powder is added: 2H₂O₂(aq) → 2H₂O(ℓ) + O₂(g). A pupil adds 0.5 g of manganese dioxide to 50 cm³ of hydrogen peroxide solution, collects the oxygen in a gas syringe and records the volume every 20 s. The table shows the results.

Volume of oxygen collected at each time.
Time / s	Volume of oxygen / cm³
0	0
20	42
40	66
60	80
80	86
100	88
120	88

(a) Calculate the average rate of the reaction over the first 20 s, in cm³ s⁻¹. [1]

cm³ s⁻¹

(b) Calculate the average rate of the reaction between 40 s and 80 s, in cm³ s⁻¹. [2]

cm³ s⁻¹

0 words · one point a mark

(d) Manganese dioxide is a catalyst. Describe how the pupil could show that the manganese dioxide is not used up in the reaction. [3]

0 words · one point a mark

Two compounds of siliconSection 2 question · 8 marks

Silicon forms covalent compounds with oxygen and with chlorine. Silicon dioxide, SiO₂, is the main compound in sand. Silicon tetrachloride, SiCl₄, is used to make very pure silicon for computer chips. In SiCl₄ the silicon atom forms a single covalent bond to each of the four chlorine atoms. The table gives some data.

Melting and boiling points of two silicon compounds.
Compound	Melting point / °C	Boiling point / °C
Silicon dioxide, SiO₂	over 1600	over 2200
Silicon tetrachloride, SiCl₄	−69	58

(a) What is the shape of a silicon tetrachloride molecule? [1]

(b) Name the type of structure silicon dioxide has. [1]

0 words · a word or a sentence

0 words · one point a mark

(d) Why does liquid silicon tetrachloride not conduct electricity? [1]

(e) Explain fully, in terms of structure and bonding, why silicon dioxide has a much higher melting point than silicon tetrachloride. [3]

0 words · one point a mark

Calcium fluorideSection 2 question · 7 marks

The mineral fluorite is calcium fluoride, CaF₂, an ionic compound with a melting point of over 1400 °C. It is made of calcium ions, Ca²⁺, and fluoride ions, F⁻.

(a) Which ion-electron equation shows a calcium atom forming a calcium ion? [1]

(b) What is the electron arrangement of a fluoride ion, F⁻? [1]

(d) State what is meant by an ionic bond. [1]

0 words · a word or a sentence

(e) Solid calcium fluoride does not conduct electricity, but molten calcium fluoride does. Explain this. [3]

0 words · one point a mark

Marble chip size and rateExperiment question · 8 marks

A pupil investigates how the size of marble chips (calcium carbonate) affects the rate of their reaction with dilute hydrochloric acid. 2.00 g of small chips is added to 50 cm³ of 1.0 mol l⁻¹ hydrochloric acid in a conical flask on a balance, with a loose cotton wool plug in the neck. The loss in mass is recorded every 30 s. The experiment is repeated with 2.00 g of large chips. The acid is in excess both times. After 10 minutes the total loss in mass is 0.88 g for both sizes.

Total loss in mass with small and large marble chips.
Time / s	Loss in mass, small chips / g	Loss in mass, large chips / g
0	0.00	0.00
30	0.42	0.20
60	0.66	0.36
90	0.80	0.50
120	0.86	0.61
150	0.88	0.70
180	0.88	0.76

(a) State one variable, other than the mass of the chips, that the pupil must keep the same. [1]

0 words · a word or a sentence

(b) Calculate the average rate of the reaction of the small chips over the first 60 s, in g s⁻¹. [2]

g s⁻¹

(d) Explain why the total loss in mass is the same for both sizes of chip. [2]

0 words · one point a mark

(e) Suggest how the pupil could make the results more reliable. [1]

0 words · a word or a sentence

(f) State why the pupil uses a loose cotton wool plug rather than a stopper. [1]

0 words · a word or a sentence