Electrochemistry

Question 1

What is the acronym and what does it represent?

Answer 1

RedCat AnOx
Reduction occurs at the cathode, Oxidation occurs at the Anode

Question 2

Describe the flow of electrons to/from the cathode/ anode.

Answer 2

electrons flow towards the cathode
‘ flow away from the anode

Question 3

who produces and consumes electrons, cathode or anode?

Answer 3

Cathode consumes electrons, anode produces electrons

Question 4

Why do cations in the salt bridge move towards the cathode?

Answer 4

Because as the ions of the cathode itself moves away, there is a loss of amount of ions occurring, therefore it is to compensate for loss of ions that goes onto rod for reduction.

Question 5

What is electricity?

Answer 5

movement of electrons

Question 6

Corrosion is

Answer 6

A term applied to the destructive oxidation of metal. It is a natural process caused by using oxidizers in the environment reacting with the metals that we have used.

Question 7

Rust is

Answer 7

A common name given to oxidation products of iron
- “rust” should only be used in relation to iron (and hence steel) oxides and hydroxides.

Question 8

Why are the results of corrosion often costly?

Answer 8

This is because the process of corrosion changes the properties from those of a metal to those of ionic compounds which are very different from the metal’s properties.

Question 9

Explain corrosion as an electrochemical process.

Answer 9

Corrosion is a spontaneous ‘redox’ process in which a metal such as iron undergoes oxidation at anode sites
and (usually) oxygen in the presence of water undergoes reduction at cathode sites.
* As such, corrosion is an electrochemical process with electrons flowing from anode sites to cathode sites and
ions flowing in directions as in galvanic cells.
- oxidation of the metal occurs at the anode
- reduction of oxygen in the presence of water occurs at the cathode
- electrons flow through the metal from anode sites -> cathode sites
- cations flow through the electrolyte towards the cathode sites
- anions flow through the electrolyte towards the anode sites

Question 10

does the oxidizing abilities of water change in the presence of oxygen?

Answer 10

much stronger

Question 11

Redox reaction of corrosion

Answer 11

o2(g)+2h2o(l)+4e- -> 4OH-(aq)
- because have both oxygen and water present

Question 12

On a piece of metal with both anodic and cathodic sites, where does damage occur?

Answer 12

Anode sites are where oxidation occurs and metal is converted into ionic compounds.

Question 13

What are some factors affecting corrosion rates and how?

Answer 13

Availability of oxygen
* Availability of water
* Temperature
* Rate increases with higher temperature
* Availability of salts
* To act as salt-bridge or electrolyte (allow cation/anion movement between
anode and cathode sites) therefore corrosion more likely in salty sea
water/near ocean than in fresh water
* Stress & Metal fatigue
* Disrupted metal lattice is more likely to act as an anode
* Exposed Surface Area
* Increased area of contact between metal and oxidising agent, gives faster
corrosion rate (e.g. steel wool rusts faster than solid nail as greater SA)
* Contact between different metals (will be discussed later)

Question 14

Where is a cathode site and anode site most likely to exist? What is this selection called?

Answer 14

where availability (concentration)
of oxygen is greatest.
Therefore, the anode is likely to be where oxygen concentration
is lowest (and where we have degradation of the metal and
corrosion occurring).
There is a potential difference between these two areas
- differential aeration

Question 15

What accelerates corrosion?

Answer 15

• salt (faster charge transfer)
• acid (fast charge transfer, combined with o2/h2o is a much stronger oxidant

Question 16

How could rusting be prevented?

Answer 16

• paint/ inert metal (prevents o2/h2o from reaching Fe surface)
• oil/ grease (also preventing them from reaching)
• sacrificial protection( galvanising)- coverage with a more reactive metal that undergoes preferential oxidation (useful for boats- don’t want the Zn to react explosively with water- Zn is more reactive than Fe
• cathodic protection (connecting to a power source and supplying a current of electrons through the iron-> redox= electron transfer, iron rusts because it loses electrons to oxygen and water)/
• using an alloy (stainless steel etc), combination of iron and sometimes less reactive substances like carbon: combining with metals/ non-metals to alter reactivity of metal

Question 17

Why do we need to figure out how to stop rusting from occurring?

Answer 17

• iron is used in infinite materials (buildings, tools etc) due to its natural abundance, affordable cost, strength, malleability and overall versatility.
• while not overly reactive, iron is not inert and readily oxidised in the presence of oxygen and water
• this forms iron (III) oxide = rust, which is brittle and weakens the structure, and can break off and damage the structure

Answer 18

forcing non favourable chemical reactions to occur (non spontaneous redox reactions
- force in occur in opposite direction
- useful for refining metals- force to regain electrons or lose them by inducing a current

Question 19

primary and secondary batteries

Answer 19

secondary cells- rechargeable (forcing reforming starting materials)
(e.g. phones, charging done via electrolysis

Question 20

similarities of electrochemistry and electrolysis

Answer 20

-both have anode and cathode
- direction of

Question 21

diffference

Answer 21

lacks of salt bridge
- unfavourable- usually chlorine won’t lose electrons
- reagent anion travel instead of stuff in salt bridge
- usually anodes produce their own electrons in a galvanic cell (in this, electrolytic cells forcibly remove electrons from the electrode creating a positive charge)
- anode is usually producing electrons spontaneously while cathode receives them, electrolytic cells remove electrons from anode, creating a positive charge
- nothing will happen until a current is applied to it

Question 22

process

Answer 22

molten= ionic solid heated up to high temp, can extract ions that way
- fo4ce electrons to be more attracted via electrical current