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Chemistry GCSE > topic 3 - acids and bases > Flashcards

topic 3 - acids and bases Flashcards

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1
Q

pH scale

A

a measure of how acidic or alkaline a substance is

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2
Q

acido

A

a substance with a pH of less than 7

they form H+ ions in water

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3
Q

the greater the concentration of H+ ions…

A

the lower the pH

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4
Q

base

A

a substance that reacts with an acid to form a salt and water

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5
Q

alkali

A

a soluble base
a substance with a pH of more than 7
forms OH- ions in the water

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6
Q

the greater the concentration of OH- ions…

A

the higher the pH

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7
Q

what are 3 examples of indicators

A

litmus
methyl orange
phenolphthalein

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8
Q

what colour is litmus in acidic, neutral and alkaline conditions

A

acidic - red
neutral - purple
alkaline - blue

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9
Q

what colour is methyl orange in acidic, neutral and alkaline conditions

A

acidic - red
neutral - yellow
alkaline - yellow

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10
Q

what colour is phenolphthalein in acidic, neutral and alkaline conditions

A

acidic - colourless
neutral - colourless
alkaline - pink

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11
Q

dissociation/ionisation of acid

A

splitting up to produce a hydrogen ion and another ion

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12
Q

acid strength indicated what

A

what proportion of the acid molecules ionise in water

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13
Q

strong acid features and examples (4)

A
  • ionises almost completely in water
  • large proportion of acid molecules dissociate to produce H+ ions
  • pH 0-2
  • nitric, sulfuric, hydrochloric
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14
Q

weak acid features and examples (4)

A
  • doesn’t fully ionise in solution
  • small proportion of acid molecules dissociate to produce H+ ions
  • pH 2-6
  • citric, ethanoic, carbonic
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15
Q

acid concentration

A

how much acid there is in a litre (dm^3) of water

measure in g/dm^3 or mol/dm^3

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16
Q

concentrated acid

A

has large amounts of acid molecules compared to the volume of water

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17
Q

dilute acid

A

has small amounts of acid molecules compared to the volume of water

18
Q

if H+ ion concentration increases by a factor of 10…

A

the pH decreases by 1

19
Q

acid + metal ->

A

acid + metal -> salt + hydrogen

20
Q

test for hydrogen

A

test for hydrogen with a lit splint

the splint will burn with a squeaky pop if present

21
Q

acid + metal carbonate ->

A

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

22
Q

test for carbon dioxide

A

using limewater

if present, the limewater will turn cloudy

23
Q

acid + metal hydroxide ->

A

acid + metal hydroxide -> salt + water

24
Q

acid + metal oxide ->

A

acid + metal oxide -> salt + water

25
Q

neutralisation reaction

A

a reaction between an acid and a base

26
Q

describe the core practical to investigate neutralisation using calcium oxide and hydrochloric acid (6)

A

1) measure a set volume of hydrochloric acid into a conical flask using a pipette or measuring cylinder
2) measure a fixed mass of calcium oxide using a mass balance
3) add calcium oxide to hydrochloric acid
4) wait for the base to finish reacting and then record pH using a pH probe or universal indicator paper
5) repeat adding calcium oxide until the acid has fully reacted (which you know as there will be solid left at the flask’s base)
6) plot a graph to see how pH changes

27
Q

common sodium, ammonium, potassium salts (solubility rules)

A

soluble

28
Q

nitrates (solubility rules)

A

soluble

29
Q

common chlorides (solubility rules) and exceptions

A

soluble

excluding silver and lead chlorides

30
Q

common sulfates (solubility rules) and exceptions

A

soluble

excluding lead, barium and calcium

31
Q

common carbonates or hydroxides (solubility rules) and exceptions

A

insoluble

excluding sodium, ammonium and potassium

32
Q

how do you prepare an insoluble salt (simple)

A

done by precipitation reaction

react two soluble salts together

33
Q

how do you prepare an insoluble salt (method) (6)

A

1) add a spatula of soluble salt to a test tube and dissolve in deionised water ; shake thoroughly to ensure salt is dissolved
2) repeat with a second soluble salt
3) tip the two solutions into a beaker and stir with a stirring rod
4) use filter paper to filter the precipitate out
5) wash the filtrate with deionised water
6) scrape onto fresh filter paper and leave to dry in an iron or desiccator

34
Q

what are the 2 ways you can prepare a soluble salt

A

using an acid and an insoluble base

using an acid and a soluble reactant

35
Q

how do you prepare a soluble salt using an acid and an insoluble base (6)

A

1) heat acid in a water bath in a fume cupboard
2) add the base to the acid in excess to ensure the acid has fully reacted
3) filter off excess solid so that only salt and water remain
4) heat solution gently to evaporate off some of the water
5) leave solution to cool and allow salt to crystallise
6) filter off solid salt and allow to dry

36
Q

what method should you use to produce hydrated copper sulfate

A

acid + insoluble base method

with copper oxide and sulfuric acid

37
Q

reaction of copper oxide and sulfuric acid to produce hydrated copper sulfate (product and equation) (describe product)

A

once the solution has crystallised, you will be left with blue crystals
CuO (s) + H2SO4 (aq) -> CuSO4 (aq) + H2O (l)

38
Q

how do you prepare a soluble salt using an acid and a soluble reactant (simple and reason)

A

using an acid-alkali titration

this is because you need to work out exactly the right amount of acid needed to neutralise the alkali

39
Q

how do you prepare a soluble salt using an acid and a soluble reactant (method) (8)

A

1) measure out set amount of acid to conical flask using a pipette
2) add a few drops of indicator with a single colour change
3) slowly add alkali to acid using burette until you reach the end point
4) carry out reaction again using identical volumes of acid and alkali but without indicator to prevent contamination
5) the solution that remains is only salt and water
6) evaporate water off slowly
7) leave salt to crystallise
8) filter off salt and allow to dry into a pure, dry salt

40
Q

end point

A

the point during a titration when an indicator shows that the amount of reactant necessary for a complete reaction has been added to a solution

Chemistry GCSE (15 decks)

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