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A Level Chemistry > Chp 2 - Acid/base & Redox Reactions > Flashcards

Chp 2 - Acid/base & Redox Reactions Flashcards

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1
Q

Rules of oxidation numbers?

A

1) unreacted elements have ON= zero
2) ions have ON= charge
3) compounds have total ON = zero
4)elements have a maximum ON as their group number

Element exceptions:
Hydrogen - 1+
But -1 in metal hydrides
Oxygen. - mostly -2
Is -1 in hydrogen peroxide. (H2O2)
Can be +2 with fluorine
Fluorine. -always -1 (as most electronegative)

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2
Q

Roman numerals indicate what?

A

The magnitude of oxidisation number when an element may have compounds/ions with different oxidisation numbers

Also indicates the charge of the ions of that element in the compound
E.g iron (II) & iron (III)
Chlorate (I) & chlorate (III)

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3
Q

When does oxidation occur?

A

When an element/ compound/ ion either
1) loses an electron
2) oxidisation number becomes more positive

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4
Q

when does reduction occur?

A

When an element/ compound/ ion either
1) gains an electron
2) oxidisation number becomes more negative

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5
Q

Which reactants are the reduction agent vs oxidation agent?

A

Reduction agent - the one that is oxidised
Oxidisation agent- the one that is reduced

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6
Q

Steps to balance half equations (with oxygen)?

A
  1. Balance the Oxygens using H2O on the products side
  2. Balance the H2Os using H+ ions (on reactant side)
  3. Balance the charges of both side using Electrons (e-) on product side
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7
Q

Formula for hydrochloric acid

A

HCl

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8
Q

Formula of sulfuric acid

A

H2SO4

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9
Q

Formula of nitric acid

A

HNO3

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10
Q

Formula for ethanoic acid

A

CH3COOH

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11
Q

Formula for sodium hydroxide (alkali)

A

NaOH

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12
Q

Formula for potassium hydroxide (alkali)

A

KOH

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13
Q

Formula for ammonia (alkali)

A

NH3

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14
Q

Explain Strong vs weak acids/alkalis

A

Strong - releases all available ions in aq solution (fully dissociated)

Weak- partial dissociation occurs

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15
Q

When neutralisation occurs?

A

Neutralisation occurs when
- any aqueous H+ and OH- ions react to from H2O
- acids react with bases (carbonates, metal oxides, alkalis) to from salts

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16
Q

What do
I) acids
Ii) alkalis

release in solution

A

ACIDS
H+ ions

ALKALI
OH-

17
Q

Acid +base

A

Salt +water

18
Q

Acid + carbonate

A

-> salt + carbon dioxide + water

19
Q

Acid + metal

A

-> salt + hydrogen gas

20
Q

How to do titrations

A
  1. Use a know concentration solution (standard solution
  2. The know concentration solution is gradually added to a know volume of unknown concentration containing an indicatior
  3. Use a pipette to add 25 cm3 of acid to a conical flask. Add a few drops of indicator.
  4. Pour alkali into the burette. Record the initial burette volume.
  5. Complete a trial titre. The conical flask should be swirled constantly above a white tile.
    Stop adding the alkali as soon as the end point is reached. Record the final burette
    volume.
  6. Repeat the titration until two concordant results are obtained. Add alkali drop by drop
    near the end point.
21
Q

What are acids

A

Proton donors

22
Q

What are bases

A

Proton acceptors

23
Q

Reaction of acid- base equation with water
Using HCl

A

HCl + H2O —> H3O+. + Cl -

24
Q

How to calculate pH using hydrogen ion concentration (for strong acids )

A

pH = -log10 [H+]

25
Q

Reaction of the ionic product of water
(Kw)

A

Kw = [H+][OH-]
At 25oc Kw = (1x10-7) x (1x10-7) = 1x10-14 mol2dm-6

26
Q

Calculation of dissociation constant Ka of weak acids

A

Ka = [H+][A-]
————-
[HA]
PKa = -log10Ka

27
Q

Ionic Reaction of ethanoic acid and water

A

CH3COOH + H2O reversable <——> CH3COO- + H3O+

28
Q

When acids react at equilibrium what is formed?

A

A conjugate base
The product that reacts with the conjugate base is the conjugate acid

29
Q

What assumptions are made for calculation with Ka of weak acids

A

1). [H+] = [A-]
The H+ ion concentration is equal to the acid ion concentration

2) we assume CH3COOH is a constant as it only changes a slight amount

30
Q

Method to calculate pH of a weak acid

A

Ka = [H+]^2
—————-
[HA]

[H+] = \/(Ka x [HA])

Then do pH = -log10[H+]

A Level Chemistry (11 decks)

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