C5 : Chemical Changes

Question 1

What is an ore? (2)

Answer 1

COMPOUND OF A METAL FOUND NATURALLY IN ROCKS IN EARTH’S CRUST
A rock containing enough metal to make it economical to extract the metal.

Question 2

What is meant by OXIDISED?

Answer 2

GAINS oxygen, LOSE electrons

Question 3

What is meant by REDUCTION?

Answer 3

LOSES oxygen, GAINS electrons

Question 4

How can we order metals in terms of reactivity? (2)

Answer 4

1. start to order them by looking at their reaction with WATER
2. to order them further, react the metal with a DILUTE ACID

Question 5

What is displacement?

Answer 5

A reaction where are more reactive metal removes a less reactive metal from its compound.

Question 6

How do you test for hydrogen?

Answer 6

If a wooden splints pops when it is immersed in hydrogen.

Question 7

Why can carbon be used to extract other metals from their ores? (2)

Answer 7

Because carbon is a non-metal but is more reactive than many metals.
It can displace the less reactive metals.

Question 8

What can hydrogen be used to extract? And why not use Carbon? (2)

Answer 8

Can extract TUNGSTEN from its oxide.

- tungsten rescued by hydrogen is very PURE

Question 9

How are metals more reactive than carbon extracted?

Answer 9

By electrolysis

Question 10

metal + acid ->

Answer 10

salt + hydrogen

TIP : reactions between metaLs and acids can only happen if the metal is more reactive than the hydrogen in the acid

Question 11

NEUTRALISATION : acid + base ->

Answer 11

salt + water

Question 12

metal oxide + acid ->

Answer 12

salt + water

Question 13

metal carbonate + acid ->

Answer 13

salt + water + CO2

Question 14

ammonia + acid ->

Answer 14

ammonium salt

Question 15

What happens to pH of a solution if the concentration of H+ increases by a factor of 10?

Answer 15

pH decreases by 1

TIP : more concentration of H+, the more acidic it is

Question 16

Difference between weak and strong acids.

Answer 16

STRONG ACIDS :
- ALL molecules are IONISED WHEN IN AQUEOUS SOLUTIONS/DISSOLVED IN WATER
- react more VIGOUROUSLY
- CO2 is given off FASTER when reacted with carbonates
- reaction with Mg FIZZES/BUBBLES
E.G - HCL, nitric acid (HNO3) , sulphuric acid ( H2SO4)

WEAK ACIDS :
- only a FRACTION of molecules are IONISED WHEN IN AQUEOUS SOLUTIONS/DISSOLVED IN WATER
- react more CALMLY
- CO2 given off SLOWER when reacted with carbonates
- reaction with Mg - GENTLE FIZZ/BUBBLES
E.G. - ethnoic acid, citric acid, carbonic acid

Question 17

REQUIRED PRACTICAL : Making soluble salts METHOD (6)

Describe a method to make pure, dry crystals of magnesium sulphate from a metal oxide and a dilute acid .

Answer 17

• use magnesium oxide and sulphuric acid
• add sulphuric acid to beaker /heat
• add Mg oxide and stir (CONTINUE ADDING UNTIL MG OXIDE IS EXCESS)
• Filter using filter paper/funnel to remove excess mg oxide
• heat solution in evaporating basin to crystallisation point (after heating leave rest of water to evaporate slowly to give larger crystals)
• leave to crystallise
• pat dry with filer paper

Question 18

List the reactivity series and what is it? (4) please send lions, cats, monkeys and cute zebras into hot countries signed Gorgon

Answer 18

Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
----Carbon -----
Zinc
Iron
Tin
Lead
---Hydrogen----
Copper
Silver
Gold
Platinum

A list of metals from most to least reactive.