Atoms & Reactions (OCR A Level Chemistry)

Exam Questions

3 hours40 questions
1a4 marks

Complete the following table.

Subatomic particle Relative Charge Relative Mass
Proton   1
Neutron    

Electron

  1 over 1836

1b
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3 marks

Complete the following table. 

Species Number of protons Number of neutrons Number of electrons 
31P      
24Na+      
37Cl      

1c2 marks

State the definition for relative atomic mass.

1d2 marks

Explain why the chemical properties of 35Cl and 37Cl are the similar.

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2a
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2 marks

Silicon exists as three isotopes, 28Si, 29Si and 30Si. In terms of the subatomic particles, state the difference between these isotopes of silicon. 

2b
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1 mark

Naturally occurring isotopes of Europium are shown in Table 1. Calculate the relative atomic mass of Europium. Give your answer to 1 d.p.

Table 1

m/z value 151 153
Abundance / % 47.8 % 52.2 %

2c
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1 mark

Figure 1 represents the mass spectrum of potassium. Use the information in the image to calculate the relative atomic mass of potassium.

Figure 1

2-1_q2c-ocr-a-as--a-level-easy-sq
2d3 marks

Potassium reacts with water in a violent reaction to form potassium hydroxide solution and hydrogen. Write a balanced symbol equation, including state symbols, for this reaction.

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3a
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3 marks

State the formula of the following compounds

i)
Ammonium hydroxide
[1]
 
ii)
Iron(II) chloride 
[1]

iii)
Copper(II) nitrate
[1]
3b3 marks

State the names of the following compounds.

i)
Fe2O3
[1]
 
ii)
Cu2O
[1]
 
iii)
FeO
[1]

3c3 marks

Write a balanced symbol equation for the reaction of magnesium oxide and hydrochloric acid to form magnesium chloride and water.

3d2 marks

Ethanol, C2H5OH, burns in oxygen to form carbon dioxide and water. Write the balanced symbol equation for this reaction.

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4a2 marks

State the definition for relative isotopic mass.  

4b
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1 mark

Determine the number of neutrons in atom of element X with mass number 58 and 26 protons.

4c
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3 marks

A sample of Antinomy was analysed in the mass spectrometer and two main isotopes were found, 121Sb and 123Sb. Use your periodic table to help you give the number of protons and neutrons in both 121Sb and 123Sb of Antimony.

4d
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1 mark

Figure 1 represents the mass spectrum of antimony. Use the information in the image to calculate the relative atomic mass of antimony. 


Figure 1

2-1_q4d-ocr-a-as--a-level-easy-sq

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5a2 marks

Silicon exists as three isotopes, 28Si, 29Si and 30Si. In terms of the subatomic particles, state the difference between these isotopes of silicon. 

5b2 marks

A student stated that the isotopes of silicon will have different chemical properties due to the different mass numbers. Is the student correct? Justify your answer.

5c
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2 marks

Beryl is a mineral composed of beryllium aluminium silicate with the formula Be3Al2Si6O18. Calculate the relative formula mass. 

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1a
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2 marks

Atoms are made up of three subatomic particles; protons, neutrons and electrons.

Particle Proton Neutron Electron
Mass / kg 1.673 x 10–27  1.675 x 10–27  9.000 x 10–31 

Using the data and the Periodic Table, calculate the mass of one atom of carbon in kg.

1b
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1 mark

12C, 13C and 14C are all isotopes of carbon.

State the difference between these three isotopes in terms of subatomic particles.

1c
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2 marks

A student claims that the different isotopes of carbon will have different chemical properties. 

Is the student correct? Explain your answer.

1d
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4 marks

Data on the relative isotopic abundance of a chemical element, E, is shown. 

Relative m/z 46 47 48 49 50
% abundance 8.02 7.31 73.81 X 5.32

 

i)
Complete the table by calculating X.

ii)
Use the data from the table and the Periodic Table to calculate the relative atomic mass, Ar, to 1 decimal place and identify element, E.

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2a
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3 marks

The Bohr model of an atom represents a central nucleus, consisting of protons and neutrons, with electrons surrounding it moving in circular orbits. 

This model was proposed by Niels Bohr in 1913 and after some further research, energy levels and sublevels were recognised, and the model was refined.  

Using your knowledge of atomic structure, complete the table for the particles found in an atom. 

Particle Relative charge Relative mass
Proton    
Neutron    
Electron    

2b
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2 marks

State the block in the Periodic Table in which silicon is placed and explain your answer.

2c
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2 marks

The graph shows the mass spectrum of a sample of silicon. 

ocr-2-1m-sq2c-silicon-mass-spectrum

Calculate the relative atomic mass, Ar, of this sample of silicon to 1 decimal place.

2d
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1 mark

Suggest why the relative atomic mass on the Periodic Table might be different to the relative atomic mass of a sample analysed using a mass spectrometer. 

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3a
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1 mark

Geraniol is a colourless oil containing two carbon-carbon double bonds and one other functional group. It is the main component of citronella oil with low water solubility, but it is soluble in common organic solvents.

State the other functional group present in geraniol.

3b
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1 mark

The mass spectrum of geraniol is shown below.

geraniol-mass-spectrum

Deduce the relative molecular mass of geraniol.

3c
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2 marks

A molecular formula of C7H54O is proposed for geraniol.

i)
Using your answer to part (b), suggest one reason why this molecular formula is possible.

ii)
Suggest one reason why this molecular formula is not possible.
3d
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3 marks

Using your previous answers, suggest a molecular formula for geraniol.

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4a
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1 mark

Silicon is a hard, brittle, blue-grey crystalline semiconductor. It is also described as a tetravalent metalloid.

State the formulae of two common silicon ions.

4b
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1 mark

The silicate ion is analogous to the carbonate ion.

Suggest the formula of the silicate ion.

4c
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2 marks

Write a balanced ionic equation to show the formation of aluminium silicate.

4d
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2 marks

Calcium silicate can be used to store or trap carbon dioxide.

Write a balanced symbol equation for this reaction showing the formation of two solid products.

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5a
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3 marks

A and B are different chemical elements, from different groups in the Periodic Table.

State why mA and nA have identical chemical properties, but mA and pB have different chemical properties. 

5b
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3 marks

An atom has twice as many protons, and twice as many neutrons, as an atom of 19F. 

Determine the chemical symbol for this atom, including the mass number, and deduce the number of electrons.

5c
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1 mark

Name an instrument which would be used to measure the relative abundances of isotopes of an element

5d
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5 marks

Explain the graph which would be produced when measuring the relative abundances of isotopes in an element.

Describe how the graph and data obtained can be used to calculate the relative atomic mass of the element in question.

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1a3 marks

In this part, you need to refer to the Periodic Table of the Elements in the Data Sheet. 

From the first 18 elements only, choose an element which fits the following descriptions:

i)
An element with an isotope that can be represented as straight M presubscript 15 presuperscript 32
[1]
ii)
The element which forms a Z2– ion with the same electron structure as Ar.
[1]
iii)
The element in Period 3 with the first four successive ionisation energies shown below, in kJ mol–1.

577 1820 2740 11600
[1]

1b
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2 marks

A sample of element G was extracted from a meteorite. Table 1 shows the relative abundance of each isotope in a mass spectrum of this sample of G. Calculate the relative atomic mass of G and suggest an identity of G. Give your answer to 1 d.p.

Table 1

Relative isotopic mass 64 66 67 68
% abundance 38.9 27.8 14.7 18.6

1c2 marks

Sometimes in the mass spectrum on G a very small peak with an m/z value of 32 is present. Explain the occurrence of this peak.

1d
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3 marks

Element G can be alloyed with tin and lead to make solder. Lead exists as four isotopes shown in Table 2 and has an Ar value of 207.241.

Calculate the relative isotopic mass of W. Give your answer to 3 significant figures.

Table 2

Relative isotopic mass W 206 207 208
% abundance 1.4 24.1 22.1 52.4

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2a2 marks

Oxyacids of chlorine include, HClO, HClO2, HClO3 and HClO4.

An acid base reaction occurs between a solution of HClO4 is added to a solution of strontium hydroxide.

Write a balanced symbol equation for this reaction including state symbols.

2b
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3 marks

Chlorine has two naturally occurring isotopes. 35Cl with a mass of 34.969 and 37Cl with a mass of 36.966.

The relative atomic mass of Cl is 35.5. Calculate the abundance of each isotope to 2 d.p. 

2c2 marks

Predict the size of the atomic radius of 35Cl relative to the atomic radius of 37Cl would be the largest. Explain your answer.

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3a2 marks

Borax is one of the most important compounds of boron. The formula of anhydrous borax is Na2B4O7

Anhydrous borax produces a sodium hydroxide and orthoboric acid, H3BO3, when dissolved in water.

Write an equation for this reaction.

3b
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5 marks

A naturally occurring sample of the element boron, B, has two isotopes 10B and 11B and a relative atomic mass of 10.8.

i)
State the definition of relative isotopic mass.
[2]
ii)
Calculate the relative abundances of both isotopes in the sample of boron, B.
[3]
3c
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3 marks

Hydrated borax powder has the formula Na2B4O7.xH2O when 2.12 g of hydrate is heated in a crucible until a constant mass is reached. The mass of the anhydrous Na2B4O7 salt is 1.11 g.

Calculate the value of x and therefore deduce the name of hydrated borax powder.

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4a3 marks

Sulfur, S8, is a yellow solid that can react with nitric acid to form sulfuric acid, a brown gas, and water.

Write a balanced symbol equation for this reaction.

4b
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3 marks

Sulfur exists as four isotopes and has a relative atom mass of 32.0928.

Figure 1 shows the relative intensities of three of these isotopes. The total relative abundance is 94.99. 

Figure 1
Sulfur mass spec graph OCR 2.1 SQ H Q4b

Calculate the relative isotopic mass of the fourth isotope of sulfur.

4c1 mark

Predict and explain whether or not the isotopes of sulfur would have the same chemical properties.

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5a
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3 marks

Copper is an easily moulded base metal that is often added to precious metals to improve their elasticity, flexibility, hardness, colour, and resistance to corrosion.

Table 1 shows the number of protons, neutrons and electrons of different isotopes and ions of copper.

Table 1
Species Protons Neutrons Electrons
    34 27
65Cu+ 29    

i)
Complete Table 1.
[2]
ii)
Give the full electron configuration of the Cu+ ion. 
[1]

5b
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3 marks

Calculate the percentage abundance of 63Cu with a mass of 62.9296 and 65Cu with a mass of 64.9278, when the average mass of the Cu isotope is 63.546.

Give your answer to an appropriate number of significant figures.

5c2 marks

Copper can form a salt with chlorine to form copper(II) chloride. This reacts with sodium phosphate to form two different salts only.

Write a balanced equation for this reaction.

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