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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Syllabus Edition
First teaching 2023
First exams 2025
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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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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Silicon reacts with chlorine to produce silicon tetrachloride.
How many moles of chlorine are needed to react with 1 mole of silicon?
2
3
4
5
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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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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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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?
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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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What is the correct order of the decreasing melting points of the four chlorides shown?
HCl MgCl2 CCl4 S2Cl2
Highest melting point 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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Which graph correctly shows the relative melting points of period 3 elements plotted against their relative electronegativities?
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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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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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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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An element X reacts according to the following sequence.
What could be element X?
Mg
Si
Al
P
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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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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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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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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)?
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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