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A Level Chemistry > Module 2: Chapter 4 - Acids and Redox > Flashcards

Module 2: Chapter 4 - Acids and Redox Flashcards

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1
Q

What are concordant results?

A

Results within 0.10 cm³ of each other

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2
Q

What is the general ionic equation for a precipitation reaction?

A

Aqueaous Ions (aq) -> insoluble solid (s)

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3
Q

What is a precipitation reaction?

A

A reaction between soluble ions which form an insoluble solid known as a precipitate

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4
Q

What is the general ionic equation for a neutralisation reaction beween an acid and an alkali?

A

H⁺ (aq) + OH⁻ (aq) -> H₂O(l)

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5
Q

What is the general ionic equation for a neutralisation reaction beween an acid and a carbonate?

A

2H⁺ (aq) + CO₃²⁻ (aq) -> H₂O (l) + CO₂ (g)

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6
Q

What is the general ionic equation for a neutralisation reaction beween an acid and a hydrogencarbonate?

A

H⁺ (aq) + HCO₃⁻ (aq) -> H₂O (l) + CO₂ (g)

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7
Q

What is hydrogencarbonate (HCO₃⁻) more commonly known as?

A

Bicarbonate

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8
Q

What is a strong acid?

A

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

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9
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. It partially dissociates in aqueous solution.

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10
Q

What is the equation for ethanoic acid dissociating?

A

all state symbols should be (aq)

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11
Q

What is a base?

A

A substance which neutralises an acid to form a salt

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12
Q

What are the types of bases?

A
  • Metal oxides
  • Metal hydroxides
  • Metal carbonates
  • Ammonia solution
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13
Q

What is an alkali?

A

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

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14
Q

How do you name a salt from a neutralisation reaction?

A

The start of the name comes from the base, the ending comes from the aci8d

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15
Q

Sulfuric acid is a strong acid, explain why it does not dissociate as expected.

A

H₂SO₄ is a strong acid, therefore it first dissociates by the following equation:
H₂SO₄ (aq) -> H⁺ (aq) + HSO₄⁻(aq).
However, the resulting HSO₄⁻ ion is a weak acid and therefore dissociates by the following equation:
HSO₄⁻(aq) ⇌ H⁺ (aq) + SO₄²⁻(aq)

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16
Q

What are the equations for sulfuric acid dissociating?

A
  1. H₂SO₄ (aq) -> H⁺ (aq) + HSO₄⁻(aq)
  2. HSO₄⁻(aq) ⇌ H⁺ (aq) + SO₄²⁻(aq)
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17
Q

Is phosphoric acid a strong acid or a weak acid?

A

A strong acid

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18
Q

What are the equations for phosphoric acid ionising?

A
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19
Q

What is titration?

A

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

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20
Q

What can titration be used for?

A
  • Finding the concentration of solution
  • Identification of unknown chemicals
  • Finding the purity of a substance
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21
Q

What is a burette reading to?

A

Always to 2 decimal points, ending in a 5 or a 0 as it is measured to the nearest half division

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22
Q

What colour is phenolphtalein in an alkaline solution?

A

Pink/Purple

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23
Q

What colour is phenolphtalein in a neutral solution?

A

Colourless

24
Q

What colour is phenolphtalein in an acidic solution?

A

Colourless

25
Q

What colour is methyl orange in an alkaline solution?

A

Yellow

26
Q

What colour is methyl orange in a neutral solution?

A

Orange

27
Q

What colour is methyl orange in an acidic solution?

A

Red

28
Q
A

n = 1

29
Q

What is the equation for % uncertainty?

A

(number of readings x uncertainty) / reading

30
Q

What is the oxidation state/number?

A

A measure of the number of electrons that an atom uses to bond with atoms of another element.

31
Q

What are the rules for assigning oxidation states?

A
  • On simple ions, the oxidation state is the charge on the ion
  • In elements, the oxidation number is 0
  • The total of the oxidation states must equal to the overall charge on the species
  • In molecules and more complex ions, the more electronegative element is assumed to be the negative ion (meaning a normally negative ion can have a positive oxidation number)
  • H is nearly always +1 and oxygen -2
  • Fluorine is always -1
32
Q

When is the oxidation number of H not +1?

A

When bonded with metals or Boron, the oxidation number is then -1

33
Q

When is the oxidation number of O not -2?

A

When bonded with Fluorine (where it is +2) or in H2O2 (where it is -1)

34
Q

What is oxidation?

A
  • The gain of oxygen
  • The loss of electrons
  • Increase in oxidation number
35
Q

What is reduction?

A
  • The loss of oxygen
  • The gain of electrons
  • Decrease in oxidation number
36
Q

What happens to the oxidation number when something is oxidised?

A

The oxidation number increases

37
Q

What happens to the oxidation number when something is reduced?

A

The oxidation number decreases

38
Q

How can you use oxidation numbers to determine whether a reaction is redox or not?

A

Identify all the oxidation numbers of products and reactants. Use these to see if any atoms have gained electrons (reduced) or lost electrons (oxidation). If there has been both a reduction and an oxidation reaction then it is a redox reaction

39
Q

What is a disproportionation reaction?

A

A disproportionation reaction is a redox reaction in which the same element is both oxidised and reduced

40
Q

What is the oxidising agent?

A

A reagent that oxidises another species by taking electrons from them and is therefore reduced itself

41
Q

What is the reducing agent?

A

A reagent that reduces another species by adding electrons to it and is therefore oxidised itself

42
Q

How do you write a half equation?

A
  1. Calculate the oxidation states on each side of the equation
  2. Balance the element changing oxidation state
  3. Balance electrons in respect to changing oxidation states (always do +e)
  4. Sort out O’s, for every O gained/lost add an H₂O molecule
  5. Sort out H’s, for every H gained/lost add an H⁺ ion
  6. Check to see if the total electric charge on the left is equal to the total electric charge on the right
43
Q

Write the half equation for:
Cr₂O₇²⁻ -> Cr³⁺

A

Cr₂O₇²⁻ + 6e⁻ + 14H⁺ -> 2Cr³⁺ + 7H₂O

44
Q

Write the half equation for:
N₂ -> NO₃⁻

A

N₂ + 6H₂O -> 2NO₃⁻ + 10e⁻ + 12H⁺

45
Q

Write the half equation for:
S₂O₃²⁻ -> S

A

S₂O₃²⁻ + 4e⁻ + 6H⁺-> 2S + 3H₂O

46
Q

Write equations for the partial and complete neutralisation reactions of carbonic acid (H₂CO₃) with sodium hydroxide

A

Partial: NaOH(aq) + H₂CO₃(aq) -> NaHCO₃(aq) + H₂O(l)
Complete: 2NaOH(aq) + H₂CO₃(aq) -> NaCO₃(aq) + 2H₂O(l)

47
Q

Why is sodium hydrogencarbonate known as an acid salt?

A
48
Q

HARD QUESTION

A

The Mn in MnO₄⁻ has an oxidation state of 7+ and Mn²⁺ has an oxidation state of 2+, therefore there is a change of 5 electrons. If we have 8 moles of MnO₄⁻ then it is a change of 40 electrons. 5 Moles of N₂O₂²⁻ contrains 10 moles of N, therefore the oxidation number of each N changes by 4 electrons. Since the oxidation number of N in N₂O₂²⁻ is 1+, the new oxidation number must be 5+. Therefore the second product of the reaction is NO₃⁻

49
Q

Use oxidation states to determine the molar ratio in which these species react:
MnO₄⁻ reacts with SO₃²⁻ to Form Mn²⁺ and SO₄²⁻

A

2:5

50
Q

Use oxidation states to determine the molar ratio in which these species react:
Cr₂O₇²⁻ reacts with Fe²⁺ to form Cr³⁺ and Fe³⁺

A

1:6

51
Q

Where is the sign placed in the oxidation number?

A

Before the number, ie -1, +3, -5

52
Q

How are roman numerals used in respect to oxidation numbers?

A

Roman numerals are used in the names of compounds of elements that form ions with different charges. The roman numeral shows the oxidation number of the element (without a +- sign). i.e. Iron (II) represents Fe²⁺, Nitrate (III) represents NO₂⁻

53
Q

What is the modern name of nitrite (NO₂⁻)?

A

Nitrate (III)

54
Q

What is the modern name of nitrate (NO₃⁻)

A

Nitrate (V)

55
Q

Can oxidation or reduction takes place alone?

A

No, for one to occur they must both occur. Therefore, they always occur in a redox reaction

A Level Chemistry (31 decks)

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