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Alevel Chemistry OCR A > Module 2: Acids And Redox > Flashcards

Module 2: Acids And Redox Flashcards

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1
Q

Acids and bases
What are acids (short)

A

Proton donors

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2
Q

Acids and bases
What are acids (long)

A

When mixed with water they release hydrogen ions- H+

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3
Q

Acids and bases
What are strong acids

A

When an acid completely dissociates to release H+ ions in aqueous solution

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4
Q

Acids and bases
Example of strong acid

A

HCl

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5
Q

Acids and bases
Example of HCl ionising

A

HCl (aq) —> H+(aq) + Cl-(aq)

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6
Q

Acids and bases
What is a weak acid

A

An acid which only partially dissociates to release H+ ions in an aqueous solution

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7
Q

Acids and bases
Example of as weak acid

A

Ethanoic acid

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8
Q

Acids and bases

Ethanoic acid partially ionising equation

A

CH3COOH(aq) <=> H+(aq) + CH3COO-(aq)

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9
Q

Acids and bases
What does an equilibrium sign indicate in acids

A

An incomplete reaction therefore a weak acid

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10
Q

Acids and bases
Formula for hydrochloride acid

A

HCl

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11
Q

Acids and bases
Formula for sulphuric acid

A

H2SO4

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12
Q

Acids and bases
Formula for nitric acid

A

HNO3

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13
Q

Acids and bases
What are classed as bases

A

Metal oxides, metal hydroxides, metal carbonates and ammonia

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14
Q

Acids and bases
What do bases do to acids

A

Neutralise them to form salts

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15
Q

Acids and bases
What are alkalis

A

When a base dissolves in water releasing OH-ions

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16
Q

Acids and bases
Common examples of metal oxide bases

A

MgO
CaO

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17
Q

Acids and bases
Examples of common metal carbonate bases

A

Na2CO3
CaCO3
CuCO3

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18
Q

Acids and bases
Examples of common alkalis

A

NaOH
KOH
NH3

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19
Q

Acids and bases
What happens in neutralisation of acid

A

H+ ions react with a base to form a salt and neutral water

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20
Q

Acids and bases
What salt 8s produced from HCl

A

——- chloride

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21
Q

Acids and bases
What salt is produced from sulphuric acid

A

————- sulphate

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22
Q

Acids and bases
What salt is produced from nitric acid

A

———— nitrate

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23
Q

Acids and bases
What salt is produced from Ethanoic acid

A

———— Ethanoate

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24
Q

Acids and bases
What does acid and metal oxide make

A

Salt and water

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25
Q

Acids and bases
What does metal hydroxide and acid

A

Salt and water

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26
Q

Acids and bases
What does acid and alkali produced

A

Salt and water

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27
Q

Acids and bases
What is the ionic equation for neutralisation

A

H+ (aq) + OH- (aq) —> H2O(l)

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28
Q

Acids and bases
What does acid and metal carbonate produce

A

Salt and water and carbon dioxide gas

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29
Q

Acids and bases
When do you get a salt

A

When hydrogen ions in the acid area replaced by metal ions or ammonium ions from the alkali

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30
Q

Acids and bases
What are strong bases

A

Base fully dissociates in water and lots of OH-ions are released

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31
Q

Acids and bases
What are weak bases

A

Bases which partially ionise in water to release OH- ions

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32
Q

Acids and bases
Why is ammonia an exception as an alkali

A

Doesn’t directly produce OH- ions

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33
Q

Acids and bases
Why is aqueous ammonia an alkali

A

Reaction between ammonia and water produces hydroxide ions

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34
Q

Acids and bases
What does ammonia react with acids to produce

A

Ammonium salt

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35
Q

Titration
What are titrations used for

A

Finding concentration of acid or alkali solutions

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36
Q

Titration
Method

A
  1. Use a pipette and pipette filler to transfer 25.0 cm3 of known solution to a conical flask.
  2. Add a few drops of indicator to the flask.
  3. Using the funnel, rinse then fill the burette with the unknown solution and record initial
  4. Titrate theknown solution with the unknown solution , with constant swirling, until the end point is reached . This is your rough titration.
  5. Repeat your titration accurately until you have three concordant results. You may wish to keep the solution from your first accurate titration in order to achieve consistency by colour matching.
  6. Ensure that you have recorded all of your results, with burette readings to the nearest 0.05 cm3.
  7. Find titre by doing final-initial
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37
Q

Titration
Where should a reading from a burette be taken

A

Bottom of meniscus

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38
Q

Titration
To what point should a reading be taken

A

To 2dp

39
Q

Titration
What are the two main indicators

A

Methyl orange
Phenolphthalein

40
Q

Titration
What colours does methyl orange indicates

A

Turns yellow to red when adding acid to alkali

41
Q

Titration
what colour does phenolphthalein indicate

A

Turns pink to colourless when adding acid to alkali

42
Q

Titration
Why is universal indicator no use in titration

A

Colour change is too gradual

43
Q

Titration
What are titrations done with

A

Standard solutions

44
Q

Titration
What is an analyte

A

Unknown solution

45
Q

Titration
What’s a standard solution

A

A solution that has a precisely known concentration

46
Q

Titration
How do you make a standard solution

A

-Using a precise balance, carefully weigh out the required mass of solid onto a weighing boat.
-Transfer this solid to a beaker. Use some distilled water to wash any bits of solid from the weighing boat into the beaker.
-Add water to the beaker to completely dissolve the solid
-Use a glass rod to stir the solution to help the solid dissolve.
-Once the solid has dissolved, transier the solution into a volumetric flask. You’ll need to use a volumetric flask that’s the same size as the volume of solution you want to make up.
-Rinse the beaker and glass rod with water, transferring this water into the volumetric flask.
-Use water to fill the volumetric flask up to the graduation line. Use a pipette to add the final few drops to make sure you don’t add too much water and overshoot the graduation line.
-Put the lid on the flask and turn the flask over a few times to thoroughly mix the solution.

47
Q

Titration
What can you calculate from a titration

A

Concentrations

48
Q

Titration
How do you do a titration calculation

A
  1. Balance equation
  2. And in table write molratio, con, vol, mol for each of what you know *using the right units
  3. Work moles of both using con=mol/vol then mol ratio
  4. Using con=mol/vol to find concentration
49
Q

Titration
What is a polyproptic acids

A

Acids that donate more than one proton

50
Q

Titration
What is a diprotic acid

A

Acid that donates two protons

51
Q

Titration
Example of diprotic acid

A

Sulphuric acid H2SO4

52
Q

Titration
Example of triprotic acid

A

Donates three protons eg phosphoric acid H3PO4

53
Q

Titration
How does a polyproptic acid change calculating titrations

A

Need double or triple number of moles to neutralise acid

54
Q

Titration
How to convert from mol dm^-3 to g dm^-3

A

Divide by Mr

55
Q

Titration
What is aback titration used for

A

Done to analys a chase or acid that does not treat easily or quickly with a base or acid

56
Q

Titration
What is done in back titrations

A

Base or acid is treated with and excess of acid or base hen left over is then titration which can be used to work back to find about original acid or base

57
Q

Acids and bases
How can an acid be both high concentration yet a weak acid

A

Molecules only partially ions in the solution but there is still lots of acid particle in the volume of solutions

58
Q

Acids and bases
How can and acid be a dilute solution of a strong acid

A

Molecules fully ionise in solution but only few acid particles in the volume of solution

59
Q

Acids and bases
What is PH

A

Measure of number of hydrogen ions in solution

60
Q

Acids and bases
How is PH proportional to number of H+ ions

A

Directly
PH § [H+]
Down1. ^x10

61
Q

Acids and bases
How would you work it number of hydrogen ions in PH4

A

X10 ^-4

62
Q

Acids and bases
How would you work our number of hydrogen ions in PH14

A

X10 ^-14

63
Q

Acids and bases
What are spectator ions

A

Ions which don’t charge and aren’t used in a reaction

64
Q

Acids and bases
What type of reaction is acid + metal and why

A

Redox
hydrogen ions in acid gain electrons so are reduced
Metal lose electrons so are oxidised

65
Q

Acids and bases
Ionic equation for neutralisation between an acid + base

A

2H+ + O2- —> H2O

66
Q

Acids and bases
Ionic equation for neutralisation between acid + alkali

A

H+ + OH- —> H2O

67
Q

Acids and bases
Ionic equation for neutralisation between Acid + carbonate

A

2H+ + CO3 2- —> H2O + CO2

68
Q

Oxidation numbers
What’s oxidation (three defs)

A

Loss of electrons
Gain of oxygen
Loss of hydrogen

69
Q

Oxidation numbers
What’s reduction (three defs)

A

Gain of electrons
Loss of oxygen
Gain of hydrogen

70
Q

Oxidation numbers
Half equation for oxidation of magnesium

A

Mg —> Mg 2+ + 2 e-

71
Q

Oxidation numbers
Half equation for reduction of oxygen

A

1/2 O2 + 2e- —> O2-

72
Q

Oxidation numbers
What happens to atoms when they react or bond to other atoms

A

Lose or gain electrons

73
Q

Oxidation numbers
What dos the oxidation number tell you

A

How many electron an atom has donated or accepted to form an ion or to form part of a compound

74
Q

Oxidation numbers
Rule for elements

A

All uncombined element and elements bonded to identical elements have an oxidation number of 0 which means they haven’t accepted or donated any electrons

75
Q

Oxidation numbers
Rule for oxidation number of a simple monatomic ion

A

Oxidation number is the same as its charge
Eg Na+ has an oxidation number of +1 and Mg2+ has an oxidation number of +2

76
Q

Oxidation numbers
Rule for molecular ions

A

Sum of oxidation numbers is the same as the overall charge of the ion so each of the atoms within the ion will have oxidation’s number which add up to the overall charge

77
Q

Oxidation numbers
Rule for a neutral compound

A

Overall oxidation number is 0and each elements have own oxidation number which add up to 0

78
Q

Oxidation numbers
Oxidation number of oxygen and exceptions

A

Nearly always 0 except in peroxides (O2 2-) where its -1 and molecular oxygen (O2) where its 0

79
Q

Oxidation numbers
Oxidation number of hydrogen and exceptions

A

Always +1 except in metal hydrides (MH x ) where its -1 and in molecular hydrogen (H2( where its 0

80
Q

Oxidation numbers
When are roman numerals used

A

If an element can have multiply oxidation number os isn’t in its normal oxidation state eg (l) = +1, (ll) = +2 and (lll) = +3

81
Q

Oxidation numbers
What is a reducing agent

A

Provides the electrons for another substance to be reduced and itself is oxidised

82
Q

Oxidation numbers
What is an oxidising agent

A

Accepts electrons from another substance fort hate to be oxidised and itself is reduced

83
Q

Oxidation numbers
Oxidation number for metals

A

Have positive values in compounds
Value is normally that of group number
Values can go no higher than the group number

84
Q

Oxidation numbers
Oxidation numbers for non metals

A

Mostly negative based on usual ion
Can have values up to groups number
Often included in name

85
Q

Redox reactions
What happens in a redox reaction

A

Reduction and oxidation happen simultaneously

86
Q

Redox reactions
What will happen to the oxidation number is electron is lost

A

Increase by 1 for each electron

87
Q

Redox reactions
What will happen to the oxidation number is and electron is gained

A

Decrease by 1

88
Q

Redox reactions what has happened if the oxidation number has increased

A

Element has lost electron and been oxidised

89
Q

Redox reactions
What has happened if the oxidation number has decreased

A

Element had gained electrons and been reduced

90
Q

Redox reactions
Steps to balance a half equations

A
  1. Work out formula before and after
  2. Work out oxidation state of element for before and after
  3. Add electrons to one side so oxidation’s states balance
  4. If overall charge on both sides aren’t equal add H+ ions (protons) to one side to balance
  5. If still don’t balance, add water molecules to one side
91
Q

Redox reactions
Steps to construct balanced redox equations

A
  1. Write out two half equations
  2. Multiply equation s so the the number of electrons balance in both equations
  3. Add two equations together and cancel out electrons
  4. Cancel our anything else which appears on both sides
92
Q

Redox
What’s a disproportionation reaction

A

When a species is simultaneously oxidised and reduced

93
Q

Redox
What is produced when Cl2 and H2O react and what is disproportionated

A

CL2 + H2O -> HCl + HClO
Chlorine

94
Q

Redox
What is produced when 2NaOH + Cl2 react and what has been disproportionated

A

2NaOH + Cl2 -> NaCl + NaClO + H2O
Chlorine

Alevel Chemistry OCR A (13 decks)

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