Electrolysis and ionic compounds

What is an ion?

An atom/group of atoms that have gained or lost at least 1 electron.

What are cations?

Positive ions, formed when an atom loses an electron(s).

What are anions?

Negative ions, formed when an atom loses an electron(s).

Which two types of substance do you need to make an ionic compound?

A metal and a non-metal.

What substances are in a covalent bond?

Two or more non-metals.

What substances are in a metallic bond?

Two or more metals.

What does it mean if a substance has an -ide ending?

There is no oxygen in the substance.

What does it mean if a substance has an -ate ending?

There is oxygen in the substance.

What are some properties of ionic substances?

• Unreactive

• High melting and boiling points

• Most of them are soluble in water

• They conduct when molten or solid.

What is the mass number of an atom?

The number of protons and neutrons in an atom, always the bigger number.

What is the atomic number of an atom?

The number of protons and electrons in an atom.

What causes ions to be able to conduct?

The ionic lattice is broken when molten or dissolved in water, so the ions are free to move and carry charge.

What is electrolysis?

The process where ionic substances are broken down into smaller 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 electric conductor where an electric current enters or leaves an electrolyte solution.

What is a cathode?

A negative electrode that attracts cations.

What is an anode?

A positive electrode that attracts anions.

What is oxidation and where does it occur during electrolysis?

Oxidation is the loss of electrons, and occurs at the anode.

What is reduction and where does it occur during electrolysis?

Reduction is the gain of electrons, and occurs at the cathode.

How do you carry out electrolysis?

• Select two pieces of metal to use as electrodes.

• Measure and record the mass of the electrodes.

• Fill the container with ionic solution and place the electrodes inside at opposite ends.

• Run a suitable current through and leave it for twenty minutes.

• Turn off the power and rinse the electrodes off with distilled water and propanone.

• Measure and record the masses of the now dry electrodes.

What is electrolysis of melts?

When the substance is heated up until it’s molten and then the ions are decomposed.

What is electrolysis of solutions?

When the salt is dissolved in water and then is decomposed.

Are metals positive or negative ions?

Positive ions.

Are non-metals positive or negative ions?

Negative ions.

What is the order of the reactivity series? (most to least reactive)

Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, copper, silver, gold.

How do the most reactive elements react with cold water and steam?

They form hydrogen and a metal hydroxide.

How does the middle of the reactivity series react with cold water and steam?

They react very slowly (if at all) with cold water, but they react with steam to form hydrogen and a metal oxide.

How do the least reactive elements react with cold water and steam?

They don’t react with cold water or steam.

What happens in displacement reactions?

The more reactive metal displaces the less reactive metal from the compound and takes its place.

How do the most reactive elements react with acid?

Violently.

How does the middle of the reactivity series react with acid?

They react to form hydrogen and a salt solution.

How do the least reactive elements react with acid?

They don’t react.

What is an ore?

A rock that contains enough of a compound to extract the metal from it.

How are metals less reactive than carbon extracted?

The ore is heated up with carbon, which is more reactive so displaces the metal in the ore. 

How are gold, silver and platinum found?

In their native states.

How are metals more reactive than carbon extracted?

The ores are heated up until they’re molten and then electrolysis is carried out on them.

What is bioleaching?

Bacteria is grown on a low grade ore, and the bacteria produces a solution called leachate which contains metal ions. The metal is then extracted from the leachate by displacement using scrap iron, and purified by electrolysis.

What is phytoextraction?

Plants are grown that absorb metal compounds, and are burnt to form ash from which the metal is then extracted.

What are the advantages of bioleaching?

• No harmful gases are produced.

• Less damage is done to the landscape than mining.

• It conserves supplies of higher grade ores.

• It doesn’t require high temperatures.

What are the advantages of phytoextraction?

• You can extract metals from contaminated salts.

• No harmful gases are produced.

• Less damage is done to the landscape than mining.

• It conserves supplies of higher grade ores.

What are the disadvantages of bioleaching?

• Toxic substances can be produced in the process, causing damage to the environment.

• It’s a very slow process.

What are the disadvantages of phytoextraction?

• It’s more expensive than mining some ores.

• Growing plants depends on weather conditions.

• It’s a very slow process.