Diff Types of Chem Reaction P3

Question 1

What is the chemical formula for rust?

Answer 1

Fe2O3.xH2O

Question 2

Which element is required for rusting to occur?

Answer 2

Oxygen

Question 3

Which compound is required for rusting to occur?

Answer 3

Water

Question 4

In the rusting experiment what does the deliquescent material calcium chloride do?

Answer 4

It absorbs moisture

Question 5

Name 5 methods of preventing rusting

Answer 5

1. Paint
2. Oil or grease
3. galvanise
4. Sacrificial protection
5. alloy stainless steel

Question 6

What is galvanising?

Answer 6

Coating the iron in a layer of zinc, the zinc will react with oxygen and save the steel

Question 7

What is sacrificial protection?

Answer 7

A more reactive metal e.g. Magnesium is bolted to the surface of iron and it will react before the iron

Question 8

Give three features of an oxidation reaction

Answer 8

1. Gain oxygen
2. Loss of hydrogen
3. Loss of electrons

Question 9

Give three features of a reduction reaction

Answer 9

1. Loss of oxygen
2. Gain of hydrogen
3. Gain of electrons

Question 10

What would be observed when magnesium burns in air?

Answer 10

Bright white light

White ash

Question 11

Give a balanced symbol equation for magnesium burning in air.

Answer 11

2Mg + O2 –> 2MgO

Question 12

Give an ionic equation to show the movement of electrons when magnesium burns in air

Answer 12

Mg - 2e- –> Mg2+

Question 13

What is observed when copper oxide is reacted with hydrogen?

Answer 13

Black copper oxide turns to copper colour

Question 14

Give a balanced symbol equation for copper oxide reacting with hydrogen.

Answer 14

CuO + H2 –> Cu + H2O

Question 15

What is the chemical name for rust?

Answer 15

hydrated iron (III) oxide

Question 16

In the reaction

Copper oxide + hydrogen –> copper + water

Identify the reducing agent

Answer 16

Hydrogen

Question 17

Why is the excess hydrogen burnt during the experiment?

Answer 17

Hydrogen is explosive and it is burned to prevent it from escaping into the lab.

Question 18

Explain why extraction of iron in the blast furnace is a redox reaction.

Fe2O3 + 3CO —> 2Fe + 3CO2

Answer 18

Iron ore (haematite) has lost oxygen = reduction
Carbon monoxide has gained oxygen = oxidised
Iron has gained electrons Fe3+ + 3e --> Fe = reduction
Reduction and oxidation in the same reaction = REDOX

Question 19

During electrolysis extraction of aluminium from aluminium oxide (bauxite). Explain why this is a redox reaction.

Answer 19

Aluminium oxide loses oxygen = reduction
Aluminium ion gains electrons Al3+ + 3e –> Al = reduction
Oxide ion loses electrons 202- -4e –> O2 = oxidation

Question 20

In the Haber process, explain why it is a redox reaction

N2 + 3H2 –> 2NH3

Answer 20

Nitrogen gains hydrogen = reduction

Question 21

What is observed when sulfur burns in air?

Answer 21

A blue flame
Yellow solid sulfur melts
Pungent smell