Periodicity (period 3)

Question 1

When sodium is placed in cold water what happens? Write an equation and describe the reaction.

Answer 1

• 2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g)

- It exhibits effervescence.

Question 2

When magnesium is placed in cold water what happens? Write an equation and describe the reaction.

Answer 2

• Mg(s) + 2H2O(l) -> Mg(OH)2 + H2(g)

- It is a very slow reaction

Question 3

When magnesium is placed in steam what happens? Write an equation.

Answer 3

Mg(s) +H2O(g) -> MgO(s) + H2(g)

Question 4

Two period 3 elements have to be stored in a liquid to prevent them from reacting with the air. What are they and what are they stored in?

Answer 4

• Sodium -> oil

- Phosphorous -> water

Question 5

When sodium is burnt what colour flame is it? What is the oxide produced?

Answer 5

• Yellow flame

- White solid`

Question 6

When sulphur is burnt what colour flame is it? What is the oxide produced?

Answer 6

• Blue flame

- Acidic choking gas

Question 7

When one of Mg, Al, Si and P is burnt what colour flame is it? What is the oxide produced?

Answer 7

• White flame

- White solid smoke

Question 8

The metal oxides are Na2O, MgO and Al2O3 which are ionic. How would you prove that they are ionic experimentally?

Answer 8

Melt them and show they conduct electricity.

Question 9

Which of the period 3 elements have a macromolecular structure? What are the properties of a macromolecular structure?

Answer 9

• Silicon (SiO2)

- High melting point and high boiling point

Question 10

When sodium oxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 10

• Na2O(s) + H2O (l) -> 2Na+(aq) 2OH-(aq)
• pH = 13
• Bonus: this is a vigorous exorthermic reaction

Question 11

When magnesium oxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 11

• MgO(s) + H2O(l) -> Mg(OH)2 (s)
• pH = 9
• Bonus: Mg(OH)2 is sparingly soluble in water.

Question 12

When aluminium oxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 12

• No reaction

- pH = 7

Question 13

When silicon dioxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 13

• No reaction

- pH = 7

Question 14

When phosphorous oxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 14

• P4O10(s) + 6H2O(l) -> 4H3PO4(aq)

- pH = 0

Question 15

When sulphur dioxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 15

• SO2(g) + H2O(l) -> H2SO3(aq)
• pH = 3
• Bonus: vigorous exothermic reaction

Question 16

When sulphur trioxide is placed in water what happens? Write an equation for this reaction and state the pH of the solution produced.

Answer 16

• SO3(g) + H2O(l) -> H2SO4(aq)

- pH = 0

Question 17

What is the trend in pH for period 3 oxides?

Answer 17

Ionic metal oxides show basic behaviour and the non-metal covalent oxides show acidic behaviour.

Question 18

The basic oxides react with acids to form what?

Answer 18

Salts.

e.g Na2O(s) + 2HCl(aq) -> 2NaCl(aq) +H2O(l)

Question 19

What is the definition of amphoteric? Which period 3 metal oxide is amphoteric?

Answer 19

• Something that can act as both an acid and a base.

- Aluminium oxide is amphoteric.

Question 20

Give an example of aluminium oxide acting as a base.

Answer 20

-Al2O3(s) + 3H2SO4(aq) -> Al2(SO4)3 (aq) + 3H2O(l)

or

-Al2O3 + 6HCl -> 2AlCl3 + 3H2O

Question 21

What type of oxide (acidic/basic/neither) is SiO2 classified as and why?

Answer 21

-It is classified as a acidic oxide as it reacts with highly concentrated NaOH despite its strong bonds

Question 22

The acidic oxides react with bases to form what?

Answer 22

-Salts e.g: P4O10(s) + 12NaOH(aq) -> 4Na3PO4(aq) + 6H2O(l)