C5 - Chemical Changes

Question 1

Reaction of a metal and oxygen

Answer 1

• Metal + oxygen —> metal oxide
• This is an oxidation reaction (the metal is oxidised)

Question 2

What is oxidation

Answer 2

• Where a substance gains oxygen
• OR when a substance loses electrons

OILRIG

Question 3

What is reduction

Answer 3

• Where a substance loses oxygen
• OR where a substance gains electrons

OILRIG

Question 4

What tests can be done to find the reactivity series

Answer 4

• Reactions with water
• Reactions with dilute acid

Question 5

General reactivity series

Answer 5

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

Question 6

What does the reactivity of a metal depend on

Answer 6

• Its ability to lose electrons and form a positive ion

Question 7

How are metals extracted from the earth

Answer 7

• Gold is unreactive so is found as a pure metal (native metal)
• Other metals are extracted using carbon (coal) as it is cheap and abundant (if less reactive than carbon)
• Electrolysis if they are more reactive than carbon

Question 8

What is a displacement reaction with metals

Answer 8

Where a more reactive metals displaces a less reactive metal from an aqueous solution of one of its salts

Question 9

What is an acid

Answer 9

a substance that forms H+ ions in aqueous solutions
all acids contain hydrogen

Question 10

What is an alkali

Answer 10

A substance that contains OH- ions in aqueous solutions

Question 11

Reaction of reactive metals with water

Answer 11

• Metal + water —> metal hydroxide + hydrogen

This is the case for potassium, sodium, lithium and calcium

Question 12

Equation for neutralisation

Answer 12

OH-(aq) + H+(aq) —> H2O(l)

Question 13

What is a base

Answer 13

• Metals oxides and metal hydroxides than can neutralise acids, produces a salt and water

Question 14

Difference between an alkali and a base

Answer 14

• Alkalis are bases that can dissolved in water (soluble) to form aqueous solutions

Question 15

Reaction of a metal and an acid and what salts do specific acids form

Answer 15

Acid + metal —> salt + hydrogen
* HCl forms chlorides
* Sulfuric acid forms sulphates
* Nitric acid forms nitrates

Question 16

Reaction of an acid with a base or an alkali

Answer 16

acid + base/alkali —> salt + water

Question 17

Reaction of metal carbonates with an acid

Answer 17

acid + metal carbonate —> salt + water + carbon dioxide

Question 18

What is a strong acid and examples

Answer 18

• An acid that is fully ionised meaning every single molecule has split up into its ions
• This is shown by the reaction arrow being in one direction only
• Strong acids include sulfuric acid, nitric acid and hydrochloric acid

Question 19

What is a weak acid with examples

Answer 19

• An acid that partially ionised in an aqueous solution.
• These are shown by a reversible reaction arrow
• Weak acids include carbonic acid, ethanoic acid and citric acid

Question 20

How to detect pH

Answer 20

• Universal indicator - colour
• Electronic pH probes - numerical value

Question 21

Rule of the pH scale

Answer 21

As the pH decreases by one unit, the concentration of hydrogen ions increases by ten times (1 order of magnitude)

Question 22

What is the concentration of an acid and the difeference between dilute and concentrated

Answer 22

• The amount of acid molecules in a set volume
• Dilute means less molecules
• Concentrated means more

Question 23

Where does the metal ion come from in a salt

Answer 23

• The pure metal itself
• Metal oxide
• Metal hydroxide
• Metal carbonate