Chem-Electrolysis (copy)

Define electrolysis

electrolysis is the splitting of ionic compounds using electricity

What is the point of electrolyisis

To extract and purify metals

What is an electrolyte

An electrolyte is an ionic compound that is molten or dissolved in water

What happens to ions during electrolysis

they become atoms or molecules

What is a cation

a positively charged ion

What charge is the cathode

the cathode is the negatively charged electrode so it attracts cations

What is an anion

a negatively charged ion

What charge is the anode

the cathode is the positively charged electrode so it attracts anions

What does PANIC stand for?

Positive Anode Negative is Cathode

Do one of these half equations:

1.molten copper chloride

2.molten aluminium bromide

3.molten potassium chloride

Answers:

1.Cu²⁺ + 2e^- —> Cu

2Cl^- —> Cl₂ + 2e^-

2.Al³⁺ + 3e^- —> Al

2Br^- —>Br₂ +2e^-

3.K⁺ + e^- —> K

2Cl^- —>Cl₂ +2e^-

What does OIL RIG stand for (in terms of electrons)?

Oxidation

Is

Loss

Reduction

Is

Gain

Which electrode does oxidation occur at?

the anode

Which electrode does reduction occur at?

the cathode

Which forms at the cathode:

a.metal

b.non-metal

a

Which forms at the anode:

a.metal

b.non-metal

b

In an aqueous solution what forms at the cathode?

Either the metal or hydrogen ions. Whichever is less reactive.

In an aqueous solution what forms at the anode?

If there are halide ions present (group 7) then the halogen will be there. If not then oxygen.

Do one of these half equations:

1.aqueous copper chloride

2.aqueous aluminium bromide

3.aqueous potassium chloride

Answers:

1.

Core Practical : how to purify copper using copper electrodes

What is produced when a metal and an acid are reacted?

Metal salt + hydrogen

What is produced when a metal hydroxide and an acid are reacted?

Metal salt + water (neutralisation reaction)

What is produced when a metal oxide and an acid are reacted?

Metal salt + water (neutralisation reaction)

What is produced when a metal carbonate and an acid are reacted?

Metal salt + water + carbon dioxide (neutralisation reaction)

What is a displacement reaction?

When one metal displaces / replaces a less reactive metal from its solution

Are displacement reactions redox reactions?

Yes. This is because they involve a transfer of electrons resulting in changes in their oxidation states.

What is the mnemonic for the reactivity series?

Please Stop Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold.

Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold

Explain reactivity in terms of the tendency to form cations.

The higher an element is in the reactivity series the more likely they are to react and lose electrons, becoming cations. Towards the bottom of the series the elements are less reactive therefore less likely to lose electrons and become cations.

Define an ore.

An ore is a rock that contains enough of a compound to extract a metal for profit.

Which metals are found uncombined?

Very unreactive metals such as platinum and gold

When do you use extraction through carbon?

When you need to purify metals between carbon and hydrogen in the reactivity series.

What is extraction through carbon?

When, for example, there is an ore containing iron oxide it can be purified. This is because carbon is more reactive than iron so when they are heated the carbon removes the oxygen from the iron oxide forming iron and carbon dioxide.

What are the 2 main types of biological extraction?

1.Phytomining

2.Bioleaching

What is phytomining?

When special plants that absorb metal compounds (such as copper) are placed on low grade ores. These are then burnt to form ash from which copper is extracted.

Pros of phytomining

-Decontaminates polluted land

-cost effective

-carbon neutral

Cons of phytomining

-limited by plant growth rate

-limited by weather / weather dependent

What is bioleaching?

When bacteria grown on a low grade ore is used and it produces a solution containing metal ions (such as copper) called leachate. Copper is extracted from the leachate by displacement usually using scrap iron, then purifed by electtrolysis.

Pros of Bioleaching

-Very low energy cost

-reduces toxic gas emissions

Cons of Bioleaching

-Extremely slow process

-risk of toxic substances affecting groundwater