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chemistry > topic 3 - chemical changes > Flashcards

topic 3 - chemical changes Flashcards

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1
Q

which ph values are alkaline

A

greater than 7

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2
Q

what does the ph scale range from

A

0-14

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3
Q

what terms can be used to describe solutions with a ph of 7

A

neutral

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4
Q

what ph is an acid

A

0 - 6

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5
Q

what ph is an alkaline

A

8 - 14

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6
Q

a substance which forms an aqueous solution with a pH of less than 7 is defined as:

A

an acid

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7
Q

do strong acids ionise completely

A

yes

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8
Q

do weak acids ionise completely

A

no they ionise partially

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9
Q

what does an acids strength mean

A

how well it ionises (dissociates) when added to water

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10
Q

what does an acids concentration mean

A

how many molecules there are per dm3 of solution

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11
Q

what is an electrolyte

A

a liquid or solution containing an ionic compound- the ions are free to move

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12
Q

what do we do if our electrolyte is insoluble

A

melt it

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13
Q

what are electrodes

A

solid conductors

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14
Q

which electrode is positive and which is negative

A

anode - positive
cathode - negative

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15
Q

what is electrolysis

A

split compounds into their elements

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16
Q

which electrode are negative ions attracted to

A

anode

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17
Q

what happens to the charged negative ions when they reach the anode

A

they are discharged and turned into a neutral ion

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18
Q

which electrode are positive ions attracted to

A

cathode

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19
Q

what is happening to ions at the electrodes

A

they are oxidising and reducing

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20
Q

what are the equations that show reduction and oxidation called

A

half equations

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21
Q

in electrolysis which direction do the electrons travel

A

anode to cathode

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22
Q

what is reduction in terms of electrons

A

reduction is the gain of electrons

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23
Q

what is oxidation in terms of electrons

A

oxidation is the loss of electrons

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24
Q

in electrolysis why does the compound you’re trying to separate need to be molten or dissolved

A

so the ions are free to move around

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25
Q

which chemical processes are used to extract metals from their ores

A

electrolysis and reduction with carbon

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26
Q

why is electrolysis not used to extract all metals

A

why is electrolysis not used to extract all metals

27
Q

when should a metal be extracted by carbon reduction

A

when the metal is less reactive than carbon

28
Q

why is electrolysis used to extract aluminium from its ores

A

it is more reactive than carbon

29
Q

what is the name of the substance that is mixed with aluminium oxide to lower its melting point

A

cryolite

30
Q

what colour is phenolphthalein in acid and alkali

A

acid- colourless
alkali- pink

31
Q

what colour is methyl orange in acid and alkali

A

acid- red
alkali- yellow

32
Q

what is a neutralisation reaction

A

a reaction between an acid and a base

33
Q

what happens during an acid-alkali neutralisation

A

H+ ions from the acid react with OH- ions from the alkali to form water

34
Q

what is a base

A

any substance that reacts with an acid to form salt and water only

35
Q

is an alkali a soluble or insoluble base

A

soluble

36
Q

what are the products when an acid reacts with metal

A

salt and hydrogen

37
Q

what are the products when an acid reacts with metal oxide

A

salt and water

38
Q

what are the products when an acid reacts with metal hydroxide

A

salt and water

39
Q

what are the products when an acid reacts with a metal carbonate

A

salt and water and carbon dioxide

40
Q

why are metal oxides normally bases rather than alkalis

A

metal oxides are normally insoluble while alkalis are soluble

41
Q

what is the name of the salt formed from magnesium and sulphuric acid

A

magnesium sulphate

42
Q

describe the chemical test for hydrogen

A

squeaky pop test:
insert a lit splint into a test tube of gas, a squeaky pop will be heard if hydrogen is present

43
Q

describe the chemical test for carbon dioxide

A

bubble the gas through limewater, limewater will turn cloudy if co2 is present

44
Q

what method must be used to prepare a salt from an acid and soluble reactant? why?

A

titration
since both of the reactants are soluble, a titration allows you to combine the reactants exactly and avoid an excess of either reactant as this would be hard to remove

45
Q

what 3 steps are required to produce a pure, dry salt from an acid and alkali

A
  • complete a titration to find the volume of acid that reacts exactly with a set volume of alkali
  • use the titration results to mix the acid and alkali in the correct proportions
  • evaporate the water from the solution, leaving pure, dry salt crystals
46
Q

how do you carry out a titration

A

use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask
add a few drops of indicator and put the conical flask on a white tile
fill the burette with acid and note the starting volume
slowly add the acid from the burette to the alkali in the conical flask, swirling to mix
stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). note the final volume reading

47
Q

which chlorides are not soluble

A

silver chloride and lead chloride

48
Q

are all nitrates soluble

A

yes

49
Q

are all common sodium, potassium and ammonium salts soluble

A

yes

50
Q

which 3 common sulphates are insoluble

A

lead sulphate, calcium sulphate and barium sulphate

51
Q

what is a salt

A

substance produced by the reaction of an acid with a base

52
Q

which 3 carbonates and hydroxides are soluble

A

sodium, potassium and ammonium calciums and hydroxides

53
Q

why can an electrolyte carry charge

A

it is a ionic compound in a molten or aqueous state meaning that the ions are free to move

54
Q

where do charged ions in the electrolyte move to during electrolysis

A

cations (positive ions) move to the cathode (negative electrode)
anions (negative ions) move to the anode (positive electrode)

55
Q

what happens at the anode during elctrolysis

A

the anions (negatively charged ions) lose electrons to form their elements

56
Q

what happens at the cathode during electrolysis

A

the cations (positively charged ions) gain electrons to form their elements

57
Q

name the processes that occur at each electrode

A

anode (positive) - oxidation
cathode (negative) - reduction

58
Q

what is formed at each electrode

A

anode - non-metal
cathode- metal or hydrogen

59
Q

how can you predict whether a metal or hydrogen will form at the negative electrode

A

if hydrogen is above the metal in the reactivity series then the metal will form
if metal is more reactive than hydrogen then hydrogen will form

60
Q

what is formed at each electrode during the electrolysis of copper chloride solution

A

positive electrode- chlorine
negative electrode- copper

61
Q

what does oxidation mean in terms of electrons

A

loss of electrons

62
Q

what does reduction mean in terms of electrons

A

gain of electrons

63
Q

what are the formulas of common acids

A

hydrochloric acids- HCl
sulphuric acid- H2SO4
nitric acid- HNO3

64
Q

what are the formulas of common alkalis

A

sodium hydroxide- NaOH
calcium hydroxide- Ca(OH)2
lithium hydroxide- LiOH

chemistry (5 decks)

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