AQA A Level Chemistry

Topic Questions

6.1 Properties of Period 3 Elements & their Oxides (A Level only)

1a3 marks

This question is about the elements in Period 3. Write equations to show the formation of the following Period 3 oxides from their elements. Include state symbols in your equations.

i)
Sodium oxide, Na2

ii)
Phosphorus (V) oxide, P4O10

iii)
Sulfur dioxide, SO2
1b2 marks

The reaction to produce silicon dioxide is as follows:

Si (s) + O2 (g) → SiO2 (s)

A student states that this is an example of a redox reaction. Is the student correct?

Justify your answer with the use of oxidation states.

1c3 marks

State the pH values for the following Period 3 oxides when reacted with water. 

i)
Sodium oxide, Na2O

ii)
Magnesium oxide, MgO

iii)
Sulfur trioxide, SO3
1d2 marks

Write an equation to show how silicon dioxide, SiO2, reacts with hot concentrated sodium hydroxide, NaOH, to produce a neutral solution. Include state symbols in your answer.

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2a3 marks

Sodium oxide, Na2O, and magnesium oxide are both Period 3 oxides that are ionically bonded. Explain why magnesium oxide has a higher melting point than sodium oxide.

2b4 marks

Both sodium oxide and magnesium oxide are basic in character. 

i)
Write the equation, including state symbols, showing how sodium oxide can act as a base when reacted with sulfuric acid, H2SO4 (aq). 

ii)
Write the equation, including state symbols, showing how magnesium oxide can act as a base when reacted with hydrochloric acid, HCl (aq).
2c2 marks

Magnesium oxide, MgO, and sulfur trioxide, SO3, are Period 3 oxides.

State the type of bonding that exists in sodium oxide, sulfur dioxide and sulfur trioxide.

2d3 marks

Magnesium oxide can be formed when magnesium reacts with steam.

i)
Write the equation, including state symbols, for this reaction.

ii)
State two observations that would be seen when magnesium reacts with steam.

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3a2 marks

Silicon dioxide, SiO2, and phosphorus (V) oxide, P4O10, are both solid acidic oxides at 298 K.

Write an equation including state symbols showing how silicon dioxide reacts with sodium hydroxide, NaOH (aq) to produce a soluble salt and water.

3b2 marks

When phosphorus (V) oxide dissolves in water it produces phosphoric acid, H3PO4.

Write an equation including state symbols showing how phosphoric acid reacts with sodium hydroxide, NaOH (aq) to produce a soluble salt and water.

3c1 mark

State the oxidation number phosphorus in phosphoric acid, H3PO4 (aq).

3d2 marks

Sodium oxide, Na2O, is a basic oxide.

Write an equation to show how sodium oxide can form a basic solution when dissolved in water. Include state symbols in your answer.

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4a1 mark

Aluminium oxide is a Period 3 oxide and can react with both acids and bases.

State the name given to this type of compound.

4b2 marks

Write an equation to demonstrate how aluminium oxide acts as a base by reacting with hydrochloric acid, HCl. 

4c2 marks

Silicon dioxide, SiO2, is an acidic oxide of the Period three elements. In the production of iron, the high temperatures in the Blast Furnace calcium oxide, CaO, can remove silicon dioxide which is an impurity to form liquid slag.

Write an equation to show how calcium oxide can remove silicon dioxide and give the name of the compound produced.

4d4 marks

Silicon dioxide, SiO2, has a melting point of 1883 K and phosphorus (V) oxide, P4O10, has a melting point of 573 K.

In terms of structure and bonding explain the difference between the melting point of silicon oxide and phosphorus (V) oxide.

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5a1 mark

A student found that 25.00 cm3 of a 0.15 mol dm-3 solution of sodium hydroxide, NaOH (aq) required 23.20 cm3 of phosphoric acid to form a neutral solution.

Balance the following equation for the reaction that occurred during this titration

__NaOH (aq) + __H3PO4 (aq) → __Na3PO4 (aq) + __H2O (l)

5b3 marks

Calculate the concentration of the phosphoric acid used in the titration in part (a).

Give your answer to two decimal places. 

5c2 marks

The oxides of sulfur, sulfur dioxide, SO2, and sulfur trioxide, SO3, will dissolve in water to produce acidic solutions.

State the oxidation number of sulfur in both sulfur dioxide, SO2, and sulfur trioxide, SO3.

5d1 mark

Sulfur dioxide dissolves in water to give sulfurous acid, H2SO3 (aq). This solution is weakly acidic and will ionise in two stages.

Write an equation to show the first ionisation stage for this acid.

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1a4 marks

Sketch a graph on Figure 1 to show the melting points of the Period 3 oxides.

Figure 1

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1b4 marks

Explain the difference between the melting point of magnesium oxide, MgO, and aluminium oxide, Al2O3.

1c4 marks

Sodium oxide, sulfur dioxide and sulfur trioxide are Period 3 oxides.

i)
State the type of bonding that exists in sodium oxide, sulfur dioxide and sulfur trioxide.

ii)
Explain why sulfur dioxide and sulfur trioxide have different boiling points.
1d2 marks

Write an equation to show how phosphorus oxide, P4O10, reacts with the strong base sodium hydroxide, NaOH. Include state symbols in your equation. 

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2a6 marks

Sodium oxide and sulfur dioxide are separately added to water. Write equations for and observations of each reaction and state the pH of any solution formed.

2b1 mark

A concentrated solution of the compound produced when sodium oxide is added to water is heated with silicon dioxide. Write the ionic equation for this reaction. 

2c3 marks

Compound A is an oxide of a Period 3 element. It dissolves in hot, concentrated potassium hydroxide and in nitric acid, but it is insoluble in water.

i)
State the term that is used to describe the behaviour of the compound A.

ii)
Write equations, including state symbols, for the reactions of compound A with potassium hydroxide and nitric acid.
2d4 marks

2.75 g of magnesium oxide was reacted in the lab with 0.50 mol dm-3 phosphoric acid to produce a compound which can be used as a health supplement for magnesium deficiency and to maintain bone health. 5.56 g of useful product was produced.

Assuming 100% yield, calculate the percentage purity of the magnesium oxide and give your answer to a suitable number of decimal places.

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3a6 marks

Explain the difference between the structure and the pH of sodium oxide and phosphorus (V) oxide.

3b2 marks

The metallic oxides in Period 3 can react with some of the non-metal oxides in the same Period. 

i)
Write an equation for the reaction between sodium oxide and phosphorus (V) oxide.

ii)
Write an equation for the reaction between magnesium oxide and phosphorus (V) oxide.
3c3 marks

Explain the pH values of sodium oxide and magnesium oxide when reacted with water.

3d1 mark

Aluminium oxide is another metallic oxide of the Period 3 elements. Write an equation to show how this metallic oxide reacts in a different way to that of sodium oxide and magnesium oxide.

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4a1 mark

Period 3 oxides can be produced in industry through combustion of fossil fuels, as well as in the blast furnace. Write an equation, including state symbols, to show how one of these impurities can be removed by a Group 2 oxide.

4b2 marks

When the gas sulfur dioxide, SO2, reacts with water an acid is formed.

Draw the lewis diagram of the sulfur containing ion that is produced in this reaction and state the bond angle in the ion.

4c2 marks

Excess aqueous sulfur dioxide, SO2, can also react with sodium hydroxide solution, NaOH (aq), in an acid base reaction to form a sulfate (IV) salt in two stages.

Give both reactions, including state symbols, for the formation of the salt.

4d3 marks

Phosphorus pentoxide, P4O10 (s), reacts with sodium hydroxide solution, NaOH (aq), to form a phosphate salt.

i)
Write the overall equation for this reaction, including state symbols.

ii)
Using oxidation numbers, state whether the reaction is a redox reaction.

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5a3 marks

The acid-base character of the Period 3 oxides changes from sodium to sulfur. In terms of electronegativity of the Period 3 element, explain why the acid-base character changes. 

5b3 marks

Cola drinks contain phosphoric acid, H3PO4, which contributes to the taste of the drink. The acidic nature of the drink can also cause damage to tooth enamel.

A student took a 20% solution of cola which was boiled for 30 minutes using a heat plate and a magnetic stirrer and allowed to cool. They added small portions of 0.010 mol dm-3 sodium hydroxide from a burette to 30.00 cm3 of the cola solution.

A pH meter recorded the pH of the initial solution and after every addition of sodium hydroxide. The student found that it took 12.05 cm3 of sodium hydroxide to neutralise the cola solution.

i)
Suggest why the student boiled the cola solution before the experiment.

ii)
Explain why would it not be suitable for an indicator to be used when carrying out this titration. 
5c4 marks

Calculate the concentration of phosphoric acid, H3PO4, in the 20% sample of cola solution, and therefore in the original cola.

5d5 marks

When phosphorus (V) oxide reacts with water it will produce phosphoric acid.

i)

Write an equation to show the reaction between phosphoric acid and include the expected pH of the resulting solution.

ii)
Explain why the melting point of phosphorus (V) oxide is relatively low compared to most other Period 3 oxides. 

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1a2 marks

Period 3 elements all form oxides when they are reacted with oxygen.

Give an equation and two observations when magnesium is heated in oxygen.

1b2 marks

Sulfur is another Period 3 element which will burn in air.  Give an equation and two observations for this reaction. 

1c4 marks

The melting points of the highest oxides of some of the elements in Period 3 are given in Table 1

Table 1

Element

Na

Mg

Al

Si

P

S

Melting point / degreeC

1275

2852

2072

1610

300

17

i)
Explain the decrease in melting point from phosphorus (v) oxide to sulfur trioxide.

ii)
Explain why magnesium oxide has a higher melting point than sodium oxide.
1d2 marks

Explain why magnesium oxide forms a weakly alkaline solution when it reacts with water.

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2a6 marks

The oxides of Period 3 elements magnesium and phosphorus have different melting points. 

Explain this difference, using your knowledge of the structure and bonding of these oxides.

2b2 marks

Consider the following oxides.

Na2O               MgO                P4O10                SO2

State which of the oxides will form a solution with the lowest pH and which will form a solution with the highest pH.

2c3 marks

The Period 3 oxides will also react with different acids and alkalis.

Give a balanced symbol equation for the following reactions:

i)
MgO and HCl

ii)
Na2O and H2SO4

iii)
SO3 and KOH
2d5 marks

A pharmaceutical company has a waste tank of phosphoric acid (H3PO4) with a total volume of 50 000 dm3.  The phosphoric acid was formed by adding phosphorus (V) oxide (P4O10) to water. 

A 25.0 cm3 sample of this solution required 22.1 cm3 of 2 mol dm-3 sodium hydroxide solution for complete reaction. 

Calculate the mass, in g, of phosphorus (V) oxide that must have been added to the water in the waste tank.

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3a3 marks

Aluminium forms an amphoteric oxide with an ionic lattice structure.

i)
State the meaning of the term amphoteric.

ii)
Give an ionic equation to show the oxide reacting with an acid.

iii)
Give a balanced equation to show the oxide reacting with potassium hydroxide.
3b6 marks

Silicon dioxide is a white powder which forms when finely divided silicon reacts with oxygen.  It has a melting point of 1883 K and if added to water, the resulting mixture has a pH of 7. However, it is described as an acidic oxide.

i)
Describe the shape and bonding of silicon dioxide.

ii)
Explain in terms of structure and bonding why it has a high melting point.

iii)

Give an equation to represent the reaction between silicon dioxide and hot, concentrated sodium hydroxide.

3c4 marks

Sodium oxide melts at 1548 K whereas sulfur dioxide melts at 200 K.

State the structures of each oxide and explain the difference in their melting points.

3d6 marks

If sodium oxide and sulfur dioxide are dissolved in separate samples of water, they form solutions with different pH values. 

State the pH values and explain why they are produced.

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4a2 marks

Sulfur dioxide reacts with water producing sulfuric (IV) acid, whereas sulfur trioxide reacts with water producing sulfuric (VI) acid.

Give an equation for each of these reactions.

4b7 marks

The structures of two oxyacids of elements in Period 3 are shown in Figure 1 below.

Figure 1

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i)
Give the oxidation state of each Period 3 element in both Acid A and Acid B in Figure 1.

ii)
Give an equation for the formation of Acid B from an oxide of an element in Period 3.

iii)

Give the formula, including the charge, of the two anions formed from Acid A and name these anions.

4c4 marks

Phosphorus (V) oxide dissolves in water to form a solution of phosphoric (V) acid.

i)

Calculate the mass in grams, of phosphorus (V) oxide required to react with 250 cm3 of water to form a solution of phosphoric (V) acid with a concentration of 0.15 mol dm-3.

ii)
Give an equation for the reaction of phosphorus (V) oxide with magnesium oxide.
4d5 marks

Using only the elements from Period 3 answer the following questions.

i)
Name an element which forms an oxide in which it has an oxidation state of +6.

ii)

Name an oxide with a macromolecular or giant covalent structure and explain why it has a high melting point.

iii)
Name an element which burns with a yellow flame in oxygen. Give an equation for this reaction. 

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5a6 marks

Period 3 oxides all have different structure and bonding types.

i)
State the structures of phosphorus (V) oxide and aluminium oxide.

ii)
The melting points of phosphorus (V) oxide and aluminium oxide are 300 degreeC and 2072 degreeC respectively. Explain the difference.
5b4 marks

Name and draw the shape of the two anions which can be formed from sulfuric (IV) acid.

5c3 marks

State the type of bonding in sodium oxide.

Describe a method that a student could use to prove that sodium oxide has this type of bonding.

5d3 marks

Figure 1 below shows the displayed formula of sulfuric (VI) acid.

Figure 1

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i)
Name the shape the sulfuric (VI) acid molecule takes and give a value for its bond angle.

ii)

Give an equation to represent the reaction between sulfuric (VI) acid and sodium hydroxide.

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