Period 3 reactions

Question 1

Reaction of sodium with water

Answer 1

Na(s) + 2H₂O → 2NaOH(aq) + H₂(g)

Question 2

Reaction of magnesium with water

Answer 2

Mg(s) + 2H₂O(l) → Mg(OH)₂ (aq) + H₂(g)

Question 3

Reaction of magnesium with steam

Answer 3

Mg + H₂O → MgO + H₂

Question 4

Reaction of sodium with oxygen

Answer 4

2Na + 1/2O₂ → Na₂O

Question 5

Reaction of magesium and oxygen

Answer 5

2Mg + O₂ → 2MgO

Question 6

Reaction of aluminium with oxygen

Answer 6

4Al + 3O₂ → 2Al₂O₃

Question 7

Reaction of silicon with oxygen

Answer 7

Si + O₂ → SiO₂

Question 8

Reaction of phosphorous with oxygen

Answer 8

4P + 5O₂ → P₄O₁₀

Question 9

Reaction of sulphur with oxygen

Answer 9

S + O₂ → SO₂

Question 10

What is the type of reaction that all period 3 elements undergo in oxygen or water?

Answer 10

Redox

Question 11

Observations in reaction of sodium and water

Answer 11

Sodium floats on the surface

fizzing

(heat energy released)

Question 12

Name the main product formed when sodium reacts with water and give its pH value

Answer 12

Sodium hydroxide

13-14

Question 13

Does Na or Mg react faster with water?

Answer 13

Na

Question 14

Why are very few bubbles seen when magnesium reacts with water?

Answer 14

Mg is sparingly soluble

Not all of it dissolves so less hydrogen produced

Question 15

Name the main product formed when Mg reacts with water and give its pH

Answer 15

Mg(OH)₂

pH = 10

Question 16

Why does Mg react faster with steam than water?

Answer 16

Higher temp so more kinetic energy

Fully dissociates in steam

Question 17

Are the reactions of period 3 with oxygen exothermic or endothermic?

Answer 17

Exothermic

Question 18

Observation when Na reacts with oxygen

Answer 18

Burns with bright yellow flame to form white sodium oxide

Question 19

Observation when Mg reacts with oxygen

Answer 19

Burns with bright white flame and produces white powder of MgO

Question 20

Why does aluminium appear to be unreactive with air?

Answer 20

coated with protective layer of aluminium oxide

Al₂O₃ is impermeable to air/water

Question 21

What are the conditions required fot the reaction of each type of phosphorous with oxygen?

Answer 21

red must be heated before it can react with oxygen

white ignites spontaneously in air

Question 22

Why are there 2 forms of phosphorous and what are they?

Answer 22

Red and white phosphorous

Allotropes (same element, dfferent arrangment of atoms)

Question 23

What colour is phosphorous pentoxide?

Answer 23

white

Question 24

What product is formed if phosphorous reacts in a limited supply of oxygen?

Answer 24

Phosphorous trioxide

P₂O₃

Question 25

Observation when sulpur reacts with oxygen

Answer 25

Blue flame, then produces colourless SO₂

Question 26

Why is it difficult to obtain a pure sample of SO₂

Answer 26

Reacts with oxygen in air to form SO₃

(contact process)

Question 27

Why does sodium oxide react with water to form an alkaline solution?

Answer 27

Na₂O + H₂O → 2NaOH

O^2- (oxide ion) reacts with water/ accepts a proton

Na₂O acts as a base

H₂O acts as an acid

Question 28

Ionic equation showing how Al₂O₃ reacts with HCl

Answer 28

Al₂O₃ + 6H⁺ → 2Al³⁺ + 3H₂O

Question 29

Ionic equation showing how Al₂O₃ reacts with NaOH

Answer 29

Al₂O₃ + 2OH^- + 3H₂O → 2Al(OH)₄^-

Question 30

Equation for reaction of Na₂O + P₄O₁₀ in theh absence of water

Answer 30

6Na₂O + P₄O₁₀ → 4Na₃PO₄