Extracting metals and equilibria

Reactivity series image on the other side

What is a displacement reaction?

A reaction where a more reactive element replaces a less reactive element from a compound

What is an ore?

A metal found in nature that has reacted with it’s environment

What is bioleaching?

The extraction of metals using bacteria

• Bacteria grown on low grade ore and produces a solution containing metal ions called a leachate
• Metal extracted from leachate by displacement using scrap iron and purified by electrolysis

Advantages of bioleaching?

• Less damage to nature
• no harmful gases
• Doesn’t require high temperature

Disadvantages of bioleaching?

• Releases sulfuric acid and other toxic substances
• Very slow

What is phytoextraction?

• Plants are grown that absorb metal compounds into its roots

• Plant concentrates metal compounds in shoots and leaves

• Plants burned and from the ash the metal is extracted

Advantages of phytoextraction?

• No harmful gases
• Less damage to landscape
• Can extract metals from contaminated soil

Disadvantages of phytoextraction?

• Takes a long time
• more expensive than mining
• Plants depend on weather

Why is gold found in it’s natural state?

Because gold is very unreactive it doesn’t react with it’s surroundings

How can we extract some metals using carbon?

You can heat some metals with carbon. If they are less reactive than carbon they will be displaced by it so they will no longer be in a compound. This can be done using a blast furnace.

Why can ions carry charge when they are molten/dissolved but not when they are solid?

Because the ions need to move to carry charge

What is electrolysis?

The process by which ionic substances are broken down into simpler substances when an electric current is passed through them

What is an electrolyte?

An ionic substance with freely moving ions

what is an electrode?

A solid electrical conductor through which and electric current enters or leaves an electrolytic solution

What is the positive electrode called?

Anode

What is the negative electrode called?

Cathode

What kind of ions do anodes attract?

Anions (negative ions)

What kind of ions do cathodes attract?

Cations (positive ions)

What is oxidation?

• Gains oxygen

• Loss of electrons

What is reduction?

• Loss of oxygen

• Gain of electrons

What happens to cations at the cathode during electrolysis?

Metal ions (which are always cations) are always attracted to the negative cathode where they gain electrons and because neutral metal atoms

What happens to non-metal ions at the anode in electrolysis?

Non-metal ions (Which are always anions) are always attracted to the positive anode where they lose electrons to become neutral atoms

What is produced at the cathode in electrolysis (if in solution)?

• Metals below hydrogen in the reactivity series are discharged (produced)

• Metals above hydrogen are NOT discharged and hydrogen is produced instead

What is produced at the anode in electrolysis (if in solution)

• Chloride, bromide and iodide ions give chlorine, bromine and iodine respectively

• Solutions containing other ions give oxygen gas instead

What happens if the substance electrolysed is molten instead of a solution?

The metal ion and non-metal will stay the same and hydrogen and oxygen will never be produced.

What are reactions where both oxidation and reduction reactions occur?

Redox reactions

When is electrolysis used?

When a metal is more reactive than carbon, it cannot be displaced by it. Because of this we need to use electricity to separate a metal from it’s compound

Why does resistance to corrosion increase as you go down the reactivity series?

The metals get less reactive, so the ones at the bottom will not react with oxygen or water at all

Disadvantages of extracting metals?

• Uses up limited resources

• Uses a lot of energy

• damages environment

What are the advantages and disadvantages of recycling?

• Metal ores last longer

• Less energy is needed

• Fewer quarries and mines are needed

• Less land is needed

• Used metal items must be collected and transported to recycling centre

• Different metals must be removed from used items and sorted

• Recycling saves different amounts of energy depending on the metal

What are the stages of a life-cycle assessment?

• Obtaining raw materials

• Manufacturing the product

• Using the product

• Disposing of the product

What data is needed for a life-cycle assessment?

• The use of energy

• The release of waste materials

• Transport and storage

• If the raw materials are renewable or not

• If any part of the product can be recycled

• How the product is disposed of