C2.5 Salts And Electrolysis Flashcards

1
Q

What pH is neutral?

A

pH 7

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2
Q

Give an example of an acid at pH 1

A

Battery acid

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3
Q

Give an example of an alkali at pH 14

A

Bleach

Oven cleaner

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4
Q

What two methods test for pH? What’s more useful?

A

Universal indicator
Litmus paper
Universal indicator is more useful because it shows you a specific colour so you can tell whether it’s a weak or strong acid/alkali

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5
Q

What’s an ion?

A

A charged particle

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6
Q

Fill in the gaps:
When metal atoms lose electrons, they form ________ ions.
When non-metal atoms gain electrons they form ________ ions.

A
  1. Positive

2. Negative

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7
Q

What’s an acid?

A

Somethings that forms H+ ions when added to water

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8
Q

What’s an alkali?

A

It forms hydroxide ions, OH- , when added to water

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9
Q

What’s a base?

A

Anything that neutralises acids but can’t dissolve in water

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10
Q

What’s the difference between an alkali and a bass?

A

They both neutralise acids but bases can’t dissolve in water whereas alkalis can.

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11
Q

What does ‘aq’ mean?

A

A solution - something dissolved in water

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12
Q

Copper oxide + sulphuric acid ->

A

Copper sulphate + water

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13
Q

Acid + alkali (base) ->

A

Salt + water

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14
Q

Acid + metal ->

A

Salt + hydrogen

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15
Q

Acid + metal carbonate ->

A

Salt + water + carbon dioxide

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16
Q

Hydrochloric acid + copper ->

A

Copper chloride + hydrogen

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17
Q

Calcium carbonate + sulphuric acid ->

A

Calcium sulphate + water + carbon dioxide

18
Q

What happens when two soluble salts are reacted together?

A

Makes an insoluble salt

19
Q

What’s the ionic equation for neutralisation?

A

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

Acid + alkali -> water

20
Q

Define electricity (in chemistry terms)

A

Flow of charge

21
Q

Define electrolysis

A

Using electricity to separate ionic compounds

22
Q

What ions are attracted to the cathode?

What ions are attracted to the anode?

A
  1. Positive

2. Negative

23
Q

When you use electrolysis to separate copper chloride what would you see at the positive electrode? Negative electrode?

A

Positive electrode- bubbles of green/yellow gas (chlorine)

Negative electrode- copper coloured solid

24
Q

What’s the name of the negative electrode?

A

Cathode

25
Q

What’s the name of the positive electrode?

A

Anode

26
Q

Positive ions are _______ - they ______ electrons

Negative ions are ______ - they _____ electrons

A

Reduced
Gain
Oxidised
Lose

27
Q

What does OILRIG stand for 😌

A

Oxidation Is Loss (of electrons)

Reduction Is Gain (of electrons)

28
Q

What’s the half equation for sodium chloride (NaCl)

A

Na+ + e- -> Na

2Cl- -> Cl2 + 2e-

29
Q

What are the products when you electrolyse brine?

What do we use them for?

A

Chlorine - swimming pools
Hydrogen - fuels
Sodium hydroxide - cleaning substances

30
Q

What is brine?

A

Salt water

Sodium chloride dissolved in water

31
Q

When you look for the products of electrolysis what products come first on the cathode?

A
Metals below hydrogen
Then
Hydrogen
Then
Metals above hydrogen
32
Q

When you look for products of electrolysis what comes first on the anode?

A
Halogens (group 7)
Then
Hydroxide (oxygen)
Then
All other negative ions
33
Q

When you electrolysis of copper sulphate what do you see at the negative electrode? Why?

A

Copper is attracted to the cathode because copper ions are positive so they’re attracted to the negative electrode as opposites attract. The copper ions become neutral which form atoms as the copper gained two electrons. Copper ions are reduced and it becomes an atom which means it becomes solid

34
Q

When you use electrolysis to separate copper sulphate what do you see at the positive electrode? Why?

A

The anode generates bubble around it and produces oxygen because the hydroxide which are negative to the positive electrode. It’s oxidised as it loses electrons and it becomes neutral meaning oxygen is produced which evaporates meaning bubbles are formed

35
Q

What happens during electroplating?

A

The negative electrode is the object that is to be electroplated
The positive electrode is the metal you want to coat the object with
The electrolyte should be a solution of the coating metal such as its metal nitrate or sulphate

36
Q

How do you plate a metal spoon in silver?

A

The metal spoon is connected to the negative terminal of the power supply. A piece of silver is connected to the positive terminal. The electrolyte is silver nitrate solution. The spoon is then coated in silver.

37
Q

Why is electroplating useful?

A

Gives the object a protective layer - resistant to corrosion
Looks nicer (jewellery)
Cheaper to coat an object in gold/silver than the whole object being made of the metal

38
Q

When we extract aluminium, why does aluminium oxide have to be molten?

A

So the ions can move freely and separate easily to the electrodes

39
Q

Why is cryolite added when we extract aluminium?

A

To lower the melting point - less energy uses - cheaper

40
Q

When you extract aluminium why do you have to regularly replace the carbon anodes?

A

They react with the oxygen and create carbon dioxide which wears the anodes away

41
Q

What are the half equations for aluminium oxide (Al2O3)?

A

Al3+ +3e- -> Al

2O2- -> O2 + 4e-