CC8 - Acids And Alkalis Flashcards

1
Q

what is the PH scale

A

a measure of how acidic or alkaline a substance is

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2
Q

what is the PH of a neutral substance

A

7

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3
Q

what are acids

A
  • a substance with a PH less than 7
  • forms H+ ions in water
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4
Q

explain the strength of an acid in terms of H+ ions

A
  • stronger acids have a higher concentration of H+ ions
  • as the concentration of H+ ions increases, the PH of the acid decreases
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5
Q

what is a base

A

a substance that reacts with an acid to produce salt and water only

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6
Q

what is an alkali

A
  • a base that is soluble in water
  • have PH greater than 7
  • form OH- ions in water (hydroxide ions)
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7
Q

explain the strength of an alkali in terms of OH- ions

A
  • stronger alkalis have a greater concentration of OH- ions
  • as the concentration of OH- ions increases, the PH of the alkali increases
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8
Q

what is an idicator

A

a dye that changes colour depending on whether the PH of a substance is above or below a certain PH

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9
Q

colours of universal indicator in: acids, neutral, alkalis

A

acid: strong = red, weak = yellow
neutral: green
alkali: strong = purple, weak = blue

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10
Q

colours of litmus indicator in: acids, neutral, alkalis

A

acid: red
neutral: purple
alkali: blue

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11
Q

colours of methyl orange indicator in: acids, neutral, alkalis

A

acid: red
neutral: yellow
alkali: yellow

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12
Q

colours of phenolphthalein indicator in: acids, neutral, alkalis

A

acid: colourless
neutral: colourless
alkali: pink

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13
Q

what is the reaction between an acid and a base called

A

neutralisation

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14
Q

neutralisation rection formula

A

acid + base —–> salt + water

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15
Q

ionic equation of neutralisation reactions in aqueous solutions

A

H+ + OH- —–> H20

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16
Q

what is the PH of the products of a neutralisation reaction, why

A

PH 7
- the concentration of H+ and OH- ions is equal

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17
Q

test for carbon dioxide

A

test - bubble the gas through limewater
result - if CO2 is present, the limewater will turn cloudy

18
Q

test for hydrogen

A

test - hold a lit splint to the gas
result - if hydrogen is present, there will be a ‘squeaky pop’

19
Q

what can all acids do in a solution

A
  • dissociate (ionise)
20
Q

what does it mean when an acid dissociates

A

the acid splits up to produce a hydrogen ion and another ion

21
Q

what is a strong acid

A
  • when all of the molecules split to form H+ ions
  • fully dissociated
22
Q

what is a weak acid

A
  • when only some of the molecules split to form H+ ions
  • partially dissociated
23
Q

what is special about the ionisation of weak acids

A

the reaction is reversible
- equilibrium lies to the left as only some molecules release H+ ions

24
Q

what is a dilute acid

A

when there is a small proportion of acid molecules compare to the volume of water per g dm-3
- strong acids can be dilute as concentration is the number of dissolved acid molecules not the number of molecules that have dissociated to produce H+ ions

25
Q

what is a concentrated acid

A

when there is a large proportion of acid molecules compare to the volume of water per g dm-3
- weak acids can be concentrated as concentration is the number of dissolved acid molecules not the number of molecules that have dissociated to produce H+ ions

26
Q

about salts

A
  • formed during neutralisation reactions
  • ionic compunds
27
Q

what salts do hydrochlorid acid, sulfuric acid and nitric acid generally produce

A

hydrochloric acid: chloride salts
sulfuric acid: sulfate salts
nitric acids: nitrate salts

28
Q

word formula for the reaction between: acid and metal oxide

A

acid + metal oxide —–> salt + water

29
Q

word formula for the reaction between: acid and metal hydroxide

A

acid + metal hydroxide —–> salt + water

30
Q

word formula for the reaction between: acid and metal

A

acid + metal —–> salt + hydrogen

31
Q

word formula for the reaction between: acid and metal carbonate

A

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

32
Q

where does the noise of the ‘squeaky pop’ come from in a test for hydrogen

A

the hydrogen burning with oxygen in the air to form water

33
Q

what happens to the PH if the concentration of H+ ions increases by factor 10

A

PH decreases by 1 (stronger acid)
- for each addition factor of 10 the H+ ions increases by the PH decrease 1 more
eg. factor 100 = PH decreases by 2

34
Q

what happens to the PH if the concentration of H+ ions decreases by factor 10

A

PH increases by 1 (weaker acid)
- for each addition factor of 10 the H+ ions decrease by the PH increases 1 more
eg. factor 100 = PH increases by 2

35
Q

what does how you make a salt depend on

A

whether it is soluble or insoluble

36
Q

what do soluble and insoluble salts form when two solutions are mixed

A
  • soluble salts: in solution
  • insoluble salts: a precipitate
37
Q

are common salts of sodium, potassium and ammonium soluble or insoluble

A

soluble

38
Q

are nitrates soluble or insoluble

A

soluble

39
Q

are common chlorides soluble or insoluble

A

soluble except: silver chloride and lead chloride

40
Q

are common sulfates soluble or insoluble

A

soluble except: lead sulfate, barium sulfate and calcium sulfate

41
Q

are common carbonates and hydroxides soluble or insoluble

A

insoluble except: sodium, potassium and ammonium ones

42
Q

how to make a pure dry sample of an insoluble salt

A
  • precipitation reaction
  • react the right two soluble salts together