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Chemistry A-Level > Acids and Redox (Chapter 4) > Flashcards

Acids and Redox (Chapter 4) Flashcards

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1
Q

What do all acids contain?

A

Hydrogen

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2
Q

Define an acid

A

A substance that releases H+ ions in aqueous solution

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3
Q

What happens when an acid is dissolved in water?

A

It releases H+ ions as protons into the solution

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4
Q

Give an example equation of an acid forming

A

HCl(g) + aq (represents excess of water) = H+(aq) + Cl-(aq)

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5
Q

What is a strong acid?

A

An acid that releases all of its hydrogen atoms into solution as H+ ions and completely dissociates in aqueous solution e.g. HCl

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6
Q

What is a weak acid?

A

An acid that only releases a small proportion of its available hydrogen atoms into solution as H+ ions and therefore only partially dissociates in aqueous solution

  • e.g. CH3COOH(aq) <=> H+(aq) + CH3COO-(aq)
  • the equilibrium arrow shows that the forward reaction is incomplete
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7
Q

Which proton is release as H+ in ethanoic acid?

A

The OH proton

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8
Q

What are the common acids?

A

Hydrochloric acid, sulfuric acid, nitric acid and ethanoic acid

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9
Q

What is the formula of sulfuric acid?

A

H2SO4

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10
Q

What is the formula of nitric acid?

A

HNO3

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11
Q

What is the formula of ethanoic acid?

A

CH3COOH

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12
Q

What is the name of the salt for ethanoic acid?

A

Ethanoate

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13
Q

What is the formula of ammonium ethanoate?

A

CH3COONH4

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14
Q

What are the common alkalis?

A

NaOH, KOH and NH3

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15
Q

What does a base do?

A

Neutralises an acid to form a salt

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16
Q

Give some examples of bases

A

Metal oxides/hydroxides/carbonate, NH3

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17
Q

What is an alkali?

A

A base that dissolves in water, releasing OH- ions into the solution

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18
Q

Define an alkali

A

A substance that releases OH- ions in aqueous solution

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19
Q

Give an example equation of an alkali forming

A

NaOH(s) + aq = Na+(aq) + OH-(aq)

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20
Q

What is neutralisation?

A
  • The reaction of H+ and OH- to form H20

- The reaction of acids and bases to form salts

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21
Q

What happens in the neutralisation of an acid?

A

H+(aq) ions react with a base to form a salt and neutral water
- the H+ ions from the acid are replaced by metal or ammonium ions from the base to form the salt

22
Q

What happens when an acid is neutralised by a metal oxide/hydroxide (solids)?

A

Salt and water only are formed

23
Q

What is the difference when acids are neutralised by alkalis?

A

The reactants are in solution

BUT same products (salt and water)

24
Q

What is the ionic equation for neutralisation?

A

H+(aq) + OH-(aq) = H2O(l)

25
Q

What happens when an acid is neutralised by a metal carbonate?

A

Salt, water AND CO2(g) are formed

26
Q

What is a titration?

A

A technique used to accurately measure the volume of one solution that reacts exactly with another solution

27
Q

What are titrations used for?

A

1) Finding the concentration of a solution
2) Identification of unknown chemicals
3) Finding the purity of a substance e.g. medicines and food

28
Q

What is a standard solution?

A

A solution of known concentration

29
Q

What is used to make up a standard solution?

A

A volumetric flask

30
Q

What are the two pieces of apparatus used in a titration?

A

1) Pipette (normally 25cm3)

2) Burette (normally 50cm3)

31
Q

What two things do you have to remember when using a burette?

A

1) Burette readings are recorded to the nearest half division with the bottom of the meniscus on a mark or between 2 marks
2) Each reading is measure to the nearest ±0.5cm3, therefore the reading always has 2 d.p. with the last place as 0 or 5

32
Q

What two things do you have to remember when doing a mean titre?

A

1) Use only your closest accurate titres - repeat until 2 agree within 0.10cm3
2) Mean titre to 1 d.p

33
Q

What can the oxidation number be thought of as?

A

The number of electrons involved in bonding to a different element

34
Q

What is the oxidation number for elements and why?

A

0, because in a pure element, any bonding is to atoms of the same element

35
Q

What is the oxidation number of an ion?

A

The charge

36
Q

What is the oxidation number of oxygen normally?

A

-2

37
Q

What is the oxidation number of hydrogen normally?

A

+1

38
Q

What is the oxidation number of group 1/2 ions?

A

+1/+2

39
Q

What is the oxidation number of the halogens normally?

A

-1

40
Q

What is the oxidation number of hydrogen in metal hydrides?

A

-1 e.g. NaH and CaH2

41
Q

What is the oxidation number of oxygen in peroxides?

A

-1 e.g. H2O2

42
Q

What is the oxidation number of oxygen when bonded to fluorine?

A

+2 e.g. F2O

43
Q

Sum of oxidation numbers =

A

Total charge of compound

44
Q

When are roman numerals used in naming?

A

Used in the names of compounds of elements that form ions with different charges

45
Q

What does the roman numeral show?

A

The oxidation state (number) of the element, without a sign

46
Q

What does iron(II) represent?

A

Fe2+ with an oxidation number of +2

47
Q

What does chlorate(I) represent?

A

ClO- where chlorine has an oxidation number of +1

48
Q

What is a redox reaction?

A

A reaction that involves reduction and oxidation

49
Q

What is oxidation?

A
  • The loss of electrons
  • An increase in oxidation number
  • The addition of oxygen
  • The removal of hydrogen
50
Q

What is reduction?

A
  • The gain of electrons
  • A decrease in oxidation number
  • The addition of hydrogen
  • The removal of oxygen
51
Q

Explain what has been oxidised and what has been reduced in this reaction:
Zn(s) + 2HCl(aq) = ZnCl2(aq) + H2(g)

A

Zn has been oxidised because its oxidation number has increased by +2 and it has lost electrons
H has been reduced because its oxidation number has decreased by 1 and it has gained electrons

52
Q

How do you prepare a standard solution?

A

By dissolving an exact mass of the solute in a solvent and making up the solution to an exact volume

Chemistry A-Level (27 decks)

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