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Chemistry > Properties of the period 3 elements > Flashcards

Properties of the period 3 elements Flashcards

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1
Q

Why does the melting point increase from Na+ to Al3+? (3)

A

The charge on the metal ion increases from Na+ to Al3+

The size of the metal ion decreases across the row

Therefore there is an increase in the strength of attraction between the metal ions and delocalised electrons

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2
Q

Why does silicon have the highest melting point? (3)

A

It has a macromolecular structure

With lots of covalent bonds

Which are very strong

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3
Q

Why do the non-metals in period 3 have low melting and boiling points? (3)

A

P4, S8 and Cl2 all have a simple molecular structure with Van der Waals intermolecular forces

Strength of the Van der Waals depends on the size of the molecule and S8 is largest, followed by P4 then Cl2

Argon exists as single atoms with the weakest Van der Waals out of all of them

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4
Q

Why does aluminium have the highest boiling point? (2)

A

Once silicon has been melted most of its strong covalent bonds have been broken, so boiling it requires only a little extra energy.

In the liquid state Aluminium still has strong electrostatic attraction between ions and delocalised electrons, and so still requires a large amount of energy to boil

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5
Q

Reaction of sodium with cold water:
- write the equation
- state the pH of the solution formed

A

2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
pH = 13-14

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6
Q

Reaction of magnesium with cold water:
- write the equation
- state the pH of the solution formed

A

Mg(s) + 2H2O(l) → Mg(OH)2(aq) + H2(g
pH = 9-10

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7
Q

Reaction of magnesium with steam:
- write the equation
- describe what you would observe

A

Mg(s) + H2O(g)→ MgO(s) + H2(g)
white flame
white solid

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8
Q

Reaction of chlorine with cold water:
- write the equation
- state the pH of the solution formed

A

Cl2(g) + H2O(l) —>—< HClO(aq) + HCl(aq)
pH = 2-3

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9
Q

Reaction of chlorine with cold water in the presence of bright sunlight:
- write the equation
- state the pH of the solution formed

A

2Cl2(g) + 2H2O(l) → 4HCl(aq) + O2(g
pH = 2-3

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10
Q

Reaction of sodium with oxygen to produce simple oxide and peroxide:
- write the equation
- flame colour
- precipitate colour

A

2Na(s) + ½O2(g) → Na2O(s)
Orange flame
2Na(s) + O2(g) → Na2O2 (s)
White solid

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11
Q

Reaction of magnesium with oxygen to produce simple oxide:
- write the equation
- flame colour
- precipitate colour

A

2Mg(s) + O2(g) → 2MgO(s)
Bright white flame
White solid

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12
Q

Reaction of aluminium with oxygen to produce simple oxide:
- write the equation
- flame colour
- precipitate colour

A

4Al(s) + 3O2(g) → 2Al2O3(s)
If you sprinkle aluminium powder you will get bright white flame/ sparkles
White solid

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13
Q

Reaction of silicon with oxygen to produce simple oxide:
- write the equation
- flame colour
- precipitate colour

A

Si(s) + O2(g) → SiO2(s)
Orange flame
Pure form of SiO2 is a white solid

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14
Q

Reaction of phosphorus with oxygen to produce simple oxide:
- write the equation
- flame colour
- precipitate colour

A

White P(v) P4(s) + 5O2(g) → P4O10(s)
White Phosphorous gives white flame
No ppt, White fumes produced

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15
Q

Reaction of sulfur with oxygen to produce simple oxide:
- write the equation
- flame colour
- precipitate colour

A

S(s) + O2(g) → SO2(s)
Pale blue flame
No ppt, Colourless gas

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16
Q

What is the trend in bonding across period 3? (1)

A

Across P3 the bonding changes from being Ionic on the left to covalent on the right

17
Q

Why does MgO have the highest melting point of all the P3 oxides? (3)

A

MgO has ionic bonds.

There are strong electrostatic forces of attraction between oppositely charged ions.

These require a lot of energy to overcome

18
Q

Why does Al2O3 have more covalent character then MgO? (3)

A

The Al3+ ion is smaller than the Mg2+ ion.

This means the Al3+ ion is more polarising than the Mg2+ ion.

This distorts the electron cloud around the O2- ion more so that there is more electron density shared between the two ions

19
Q

For the oxides of Phosphorus and Sulphur, why does P4O10 have the highest melting point, followed by SO3 then SO2? (3)

A

These all have simple molecular structures.

They all have Van der Waals intermolecular forces between molecules.

P4O10 is the largest molecule so has the strongest Van der Waals, whereas SO2 is the smallest so has the weakest Van der Waals

20
Q

Why does SiO2 have a high melting point? (3)

A

This has a macromolecular structure.

It has lots of covalent bonds.

Which are very strong.

21
Q

Reaction of sodium oxide with water:
- write the equation
- state the pH of the solution formed

A

Na2O(s) + H2O(l) → 2Na+(aq) + 2-OH(aq)
pH = 13-14

22
Q

Reaction of magnesium oxide with water:
- write the equation
- state the pH of the solution formed

A

MgO(s) + H2O(l) → Mg(OH)2(aq)
pH = 9-10

23
Q

Explain why sodium oxide forms an alkaline solution when it reacts with water (2)

A

Sodium oxide contains O2– ions

These O2– ions react with water forming OH– ions

24
Q

What is the pH of the solution when aluminium oxide or silicon dioxide are added to water?

A

7
Both insoluble in water and so undergo no reaction to make the water acidic or alkaline

25
Q

Reaction of phosphorus (V) oxide with water:
- write the equation
- state the pH of the solution formed
- name the solution formed

A

P4O10(s) + 6H2O(l) → 4H3PO4(aq)
pH = 1-2
Phosphoric(V) Acid

26
Q

Reaction of sulphur dioxide with water:
- write the equation
- state the pH of the solution formed
- name the solution formed

A

SO2(g) + H2O(l) → H2SO3(aq)
pH = 2-3
Sulfurus Acid / Sulfuric(IV) acid

27
Q

Reaction of sulphur trioxide with water:
- write the equation
- state the pH of the solution formed
- name the solution formed

A

SO3(g) + H2O(l) → H2SO4(aq)
pH = 0-1
Sulfuric(V) Acid

28
Q

How do the acid/base properties of the P3 oxides change going across the period? (1)

A

Across the period the oxides change from being basic to neutral to acidic

29
Q

What is the relationship between the bonding and acid/base properties of the period 3 oxides? (1)

A

The oxides which are ionically bonded tend to be alkaline

The oxides which are covalently bonded tend to be acidic

30
Q

What does the term amphoteric mean?

A

Can react with a base or an acid

31
Q

Write an equation to show how aluminium oxide can act as a base when it reacts with an acid (1)

A

Al2O3(s) + 6HCl (aq)→ 2AlCl3(aq) + 3H2O(l)

32
Q

Write an equation to show how aluminium oxide can act as an acid when it reacts with a base (1)

A

Al2O3(s) + 2NaOH (aq) + 3H2O(l)→ 2NaAl(OH)4(aq)

33
Q

Write an ionic equation for the reaction of phosphorus(V) oxide with an excess of sodium hydroxide solution (1)

A

P4O10 + 12OH– → 4PO43- + 6H2O

34
Q

Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide (2)

A

SiO2 neutralises bases.

SiO2 + 2NaOH → Na2SiO3 + H2O

35
Q

Write an equation for the reaction of sulphur (IV) oxide with water and suggest the pH value of the resulting solution (2)

A

SO2 + H2O → H2SO3
pH: 1-3

Chemistry (28 decks)

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