3.3 Acids & Alkalis

Question 1

what do acids produced when added to water?

Answer 1

H+ ions - proton donor

Question 2

what do alkali’s produced when added to water?

Answer 2

OH- ions - proton acceptor - alkali is a soluble base

Question 3

H+ ions relation to pH scale

Answer 3

strongly acidic (pH 0) - most H+ ions - 10⁰

• strongly alkali (pH 14) - least H+ ions - 10⁻¹⁴
• as numbers on pH scale go up by 1, number H+ ions decreases by a factor of 10

Question 4

what do you use to measure the pH of something?

Answer 4

universal indicator

Question 5

what does the number of hydrogen ions present in a solution depend on?

Answer 5

how ionised the acid is

Question 6

what does ionisation mean?

Answer 6

ionised means how split up the acid is - when HCL splits up into H+ and Cl-

Question 7

what happens when acid is partially ionised?

Answer 7

acid is only partially split up & hydrogen ion concentration is lower - weak acid

Question 8

draw a concentrated strong acid

Answer 8

fully dissociated - many particles

Question 9

draw a dilute strong acid

Answer 9

fully dissociated - not many particles

Question 10

draw a concentrated weak acid

Answer 10

partially dissociated - many particles

Question 11

draw a dilute weak acid

Answer 11

partially dissociated - not many particles

Question 12

blue litmus paper & red solution shows

Answer 12

acidity in a substance

Question 13

red litmus paper turns blue shows

Answer 13

alkalinity in a substance

Question 14

substance is neutral pH

Answer 14

if litmus paper used - colour doesn’t change

- if litmus solution used - turns purple

Question 15

neutralisation reaction

Answer 15

acid + base –> salt + water (+CO2)

Question 16

ionic equation for formation of water

Answer 16

H+ (aq) + OH- (aq) –> H20 (l)

Question 17

properties of salt

Answer 17

compound made of metal & non-metal

• v. high mpt
• dull + brittle

Question 18

common bases

Answer 18

• metal carbonates
• metal oxides
• metal hydroxides

Question 19

4 ways of making salts from acids:

Answer 19

acid + metal hydroxide –> salt + water
acid + metal oxide –> salt + water
acid + metal carbonate –> salt + water + CO2
(acid + metal –> salt + hydrogen)

Question 20

reacting acid with metal (to make salt) - method

Answer 20

has to be more reactive than hydrogen - not too reactive though

Question 21

reacting acid with base (to make salt) - method

Answer 21

insoluble - filtration + crystallisation

Question 22

reacting acid with alkali (to make salt) - method

Answer 22

titration

Question 23

reaction between 2 salt solutions to form an insoluble salt (to make salt) - method

Answer 23

precipitation, filtration, wash, dry

Question 24

why do you use titration?

Answer 24

to make a neutralisation reaction between a base and an acid producing a salt without any excess

Question 25

why do you do titration twice?

Answer 25

• 1st time - find amounts of reactants to use

- 2nd time - actual one

Question 26

making copper sulfate from copper (II) oxide - making salts from insoluble bases

Answer 26

1 - add insoluble copper oxide to sulfuric acid + stir - warm gently
2 - solution turns blue as reaction occurs - shows copper sulfate is being formed
3 - when reaction complete - filter solution to remove excess copper oxide
4 - evaporate some of water from filtrate + leave to crystallise

Question 27

how can insoluble salts be produced?

Answer 27

by mixing 2 soluble salt solutions together

• ions swap partners in the reaction in a displacement reaction
• the combinations of ions that produce an insoluble salt result in a precipitate forming (called precipitation reactions)

Question 28

what type of salt is always soluble?

Answer 28

nitrates

Question 29

what is the end point (titration)

Answer 29

• the point in titration where you have added the exact amount of acid / alkali where neutralisation occurs