A LevelChemistryCIETopic Questions9. The Periodic Table: Chemical Periodicity9.2 Periodicity of Chemical Properties of the Elements in Period 3

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First teaching 2023

First exams 2025

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Periodicity of Chemical Properties of the Elements in Period 3 (CIE A Level Chemistry)

Topic Questions

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11 mark

What happens to the pH of water when magnesium oxide is dissolved into it?

  • pH increases, because MgO is acidic.

  • pH decreases, because MgO is basic.

  • pH increases, because MgO is basic.

  • Nothing happens because MgO is neutral.

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21 mark

Which observations are made when a sample of phosphorus chloride, PCl5, is added to a beaker of water?

  • No visible changes are observed.

  • Steamy fumes is the only observation.

  • A white precipitate is the only observation.

  • Steamy fumes and a white precipitate are both observed.

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31 mark

Silicon reacts with chlorine to produce silicon chloride. 

How many moles of chlorine are needed to react with 1 mole of silicon?

  • 2

  • 3

  • 4

  • 5

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41 mark

During the manufacture of steel, the impurity P4O10 is removed by reacting it with calcium oxide. The only product of this reaction is a salt, calcium phosphate (Ca3(PO4)2).

In this reaction, how many moles of P4O10 will react with three moles of calcium oxide?

  • 0.5

  • 1.5

  • 3

  • 6

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51 mark

Which chlorides of Period 3 elements will form a neutral solution when added to water?

1

MgCl2

2

NaCl

3

SiCl4

  • 1 only

  • 1 and 2

  • 2 and 3

  • 1, 2 and 3

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61 mark

Use of the periodic table is relevant to this question.

Which graph correctly shows the Electronegativity of the elements Na, Mg, Al and Si, from period 3, plotted against their first ionisation energies?

  • 2-1-e-10a

  • 2-1-e-10b

  • 2-1-e-10c

  • 2-1-e-10d

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11 mark

An element X reacts according to the following sequence.

2-1-h-2What could be element X?

  • Mg

  • Si

  • Al

  • P

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21 mark

When solution X is titrated against hydrochloric acid, a neutralisation reaction occurs.

Which of the following hydroxides is not solution X?

  • Magnesium

  • Aluminium

  • Sodium

  • Phosphorous

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31 mark

G and J are oxides of different Period 3 elements.

If one mole of J is added to water, the solution formed is neutralised by exactly one mole of G. 

What could be the identities of G and J?

 

G

J

A

B

C

D

Na2O

Na2O 

Al2O3

Al2O3

SO3

P4O10

SO3

P4O10

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41 mark

Mohr’s salt is a pale green crystalline solid which is soluble in water. It contains two cations, of which one is Fe2+ and one anion which is SO42-.

The second cation was determined by heating solid Mohr’s salt with solid sodium hydroxide, and a colourless gas was evolved. The gas readily dissolved in water giving an alkaline solution.  

A grey-green solid residue was also formed, which was insoluble in water. 

Which row correctly identifies the colourless gas and the grey-green residue?

 

Residue

Gas

A

B

C

D

Fe(OH)2

Fe(OH)2

Na2SO4

Na2SO4

NH3

SO2

NH3

SO2

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51 mark

Bacteria in swimming pools are killed by adding aqueous sodium chlorate (I), NaOCl. This reacts with water to produce HOCl molecules which can breach the bacteria cell wall and kill the bacteria. The reaction below shows the reaction with water:

OCl– (aq) + H2O  begin mathsize 16px style rightwards harpoon over leftwards harpoon with blank below end style  OH– (aq) + HOCl (aq)

Under the sun’s UV rays, the OCl– ion is broken down by ultra-violet light:

    OCl– (aq) + uv light rightwards arrow Cl– (aq) + ½O2 (g) 

Which method would maintain the highest concentration of HOCl (aq)?

  • Add a solution containing chloride ions.

  • Acidify the pool water.

  • Bubble air through the water.

  • Add a solution of hydroxide ion.

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11 mark

The labels had become detached from four bottles in the laboratory. A student realised that the contents of one of them could easily be identified because in the addition of water it would not give fumes of hydrogen chloride.

Which did not give the HCl fumes?

  • AlCl3

  • SiCl4

  • PCl5

  • MgCl2

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21 mark

What is the correct order of the decreasing melting points of the four chlorides shown?

                                        HCl      MgCl2      CCl4       S2Cl2

 

Highest melting point    rightwards arrow  Lowest melting point

A

B

C

D

HCl

HCl

MgCl2

CCl4

S2Cl2

CCl4

CCl4

S2Cl2

CCl4 

S2Cl2

S2Cl2

HCl

MgCl2

MgCl2

HCl 

MgCl2

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31 mark

Which graph correctly shows the relative melting points of period 3 elements plotted against their relative electronegativities?

  • 2-1-m-5a

  • 2-1-m-5b

  • 2-1-m-5c

  • 2-1-m-5d

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41 mark

Non-metallic elements and their atoms can have the two following properties.

Property 1:     Has no paired 3p electrons 

Property 2:     Has an oxide that can form a strong acid in water

Which properties do phosphorus and sulfur have?

 

Sulfur

Phosphorus

A

B

C

D

2 only 

1 and 2  

1 and 2  

2 only

1 and 2  

2 only 

1 and 2 

1 only

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51 mark

Which properties do compounds of silicon and aluminium have in common?

  • Their oxides are amphoteric.

  • Their oxides are insoluble in water.

  • Aqueous solutions of their chlorides contain aluminium or silicon cations.

  • Their chlorides have co-ordinate bonding.

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61 mark

Period 3 elements can react with chlorine to produce the following chlorides:

MgCl2       AlCl3      SiCl4      PCl3      SCl2

Period 3 elements also react with oxygen to produce oxides.

When the oxides are produced is when the period 3 element is in its highest possible oxidation state. Which of the elements have a higher oxidation number than in the above chlorides?

  • Mg, Al, Si, P and S

  • Al, P and S

  • Mg and Si

  • P and S

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