Periodicity of Chemical Properties of the Elements in Period 3 (Cambridge (CIE) A Level Chemistry): Exam Questions

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?

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

                                        HCl      MgCl₂      CCl₄       S₂Cl₂

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

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?

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

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?

An element X reacts according to the following sequence.

What could be element X?

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

Which of the following hydroxides is not solution X?

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?

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 SO₄^2-.

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?

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    OH^– (aq) + HOCl (aq)

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

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

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