C5- Chemical changes

Question 1

ores

Answer 1

rock which contains enough metal to make it economically worthwhile to extract the metal

Question 2

oxidised

Answer 2

• oxygen added

- lost electrons

Question 3

reduction

Answer 3

• oxygen is removed

- electrons are gained

Question 4

reactivity series

Answer 4

list of elements in order of their reactivity

Question 5

half-equations

Answer 5

equation that describes reduction or oxidation

Question 6

alkalis

Answer 6

• solution has a pH value more than 7

- produce OH- ions when add to water

Question 7

acids

Answer 7

• when dissolved in water, solution has a pH value less than 7
• proton donors (H+ ion)

Question 8

electrolysis

Answer 8

breakdown of a substance containing ions by electricity

Question 9

salt

Answer 9

compound formed when some or all of the hydrogen in an acid is replaced by a metal

Question 10

neutralisation

Answer 10

• chemical reaction of an acid with a base in which a salt and water are formed
• if base is a carbonate or hydrogen carbonate, carbon dioxide is also produced in the reaction

Question 11

bases

Answer 11

• oxide, hydroxide, or carbonate of a metal that will react with an acid
• forming a salt as one of the products
• if dissolves in water, alkali
• proton (H+ ion) acceptors

Question 12

neutral

Answer 12

• solution which has a pH value which is neither acidic or alkaline
• or something that carries no overall electrical charge

Question 13

pH scale

Answer 13

number which shows how strongly acidic or alkaline a solution is

Question 14

weak acid: nature

Answer 14

acids that don’t ionise completely in aqueous solutions

Question 15

strong acid: nature

Answer 15

acids completely ionise in aqueous solutions

Question 16

salt crystal method (8)

Answer 16

• react boiling (acid) with (metal)
• add and stir in until metal is in excess
• so all acid has reacted
• filter solution with filter paper + funnel, to remove excess
• heat solution in evaporating dish over water bath
• stop heating after half liquid has evaporated (crystallisation point)
• leave saturated solution at room temp for days, so () crystal can form
• pat dry with filter paper

Question 17

substances that can react with an acid to for soluble salt

Answer 17

• alkali
• metal hydroxide
• metal carbonate
• metal oxide
• metal

Question 18

metal + acid –>

Answer 18

salt + hydrogen

Question 19

metal oxide + acid –>

Answer 19

salt + water

Question 20

metal hydroxide + acid –>

Answer 20

salt + water

Question 21

metal carbonate + acid –>

Answer 21

salt + water + carbon dioxide

Question 22

ammonia + acid –>

Answer 22

ammonium salt

Question 23

strong acid: examples

Answer 23

• hydrochloric acid
• nitric acid
• sulfuric acid

Question 24

strong acid: reaction with Mg

Answer 24

vigorous fizzing

Question 25

strong acid: reaction with carbonates

Answer 25

vigorous fizzing

Question 26

strong acid: pH of typical 1.0 mol/dm3 solution

Answer 26

0

Question 27

strong acid: colour of universal indicator with typical 1.0 mol/dm3 solution

Answer 27

red

Question 28

weak acid: examples

Answer 28

- ethanoic acid (vinegar) - citric acid (citrus fruits) - carbonic acid (rainwater, fizzy drink)

Question 29

weak acid: reaction with Mg

Answer 29

gentle fizzing

Question 30

weak acid: reaction with carbonates

Answer 30

gentle fizzing

Question 31

weak acid: pH of typical 1.0 mol/dm3 solution

Answer 31

3-4

Question 32

weak acid: colour of universal indicator with typical 1.0 mol/dm3 solution

Answer 32

orange