Electrolysis

What happens when an electrical current passes through a molten ionic compound?

The compound decomposes/breaks down

What are electrolytes?

Molten or dissolved ionic compound that conducts electicity

What is an electrode?

A rod of metal or graphite through which an electric current flows into or out of an electrolyte

What is an anode?

The positive electrode of an electrolysis cell

What is an anion?

Negatively charged ion which is attracted to the anode

What is a cathode?

The negative electrode of an electrolysis cell

What is a cation?

PAW-sitevely charged ion which is attracted to the cathode

Why can’t ionic solids be electrolysed?

Because the ions are in fixed positions and can’t move and carry the charge

What is the electron flow direction in electrolysis?

Flows from the positive terminal (anode) to the negative terminal (cathode)

What is a binary ionic compound?

A compound consisting of just 2 elements joined together by ionic bonding

What product will be at the cathode when a binary ionic compound is put through electrolysis?

Metal

What product will be at the anode when a binary ionic compound is put through electrolysis?

Non-metal

DO ELECTROLYSIS FLASHCARDS ON PMT FOR R.P

YES OR NO????

Which ore does Aluminum come from?

Bauxite

And what does bauxite contain?

Aluminum oxide

Why is Aluminum oxide dissolved in molten cryolite before electrolysis?

No reduce the melting point of Aluminum - cost effective

Why does the anode have to be replaced so frequently? (aluminum oxide)

The carbon in the graphite anodes reacts with the oxygen produced to produce CO₂ - as a result the anode wears away

What is the equation to show what is happening at the cathode? (Aluminum Oxide)

Al³⁺ + 3e^- = Al

What is the equation to show what is happening at the anode? (Aluminum Oxide)

2O^2- = O₂ + 4e^-

What is the overall equation? (Aluminum oxide)

2Al₂O₃ = 4Al + 3O₂

What are the halide ions?

Cl^-, Br^-, I^-

In Electrolysis of aqueous solutions - at the positive electrode - what happens when there are halide ions?

The halide ions discharge at the anode

In Electrolysis of aqueous solutions - at the positive electrode - what happens when there are no halide ions?

The OH^- from the water is discharged at the anode, which loses electrons and forms oxygen

What is the half-equation when OH- is discharged at the anode?

4OH^- = 2H₂O + O₂ + 4e^-

In Electrolysis of aqueous solutions - at the negative electrode - what happens when there is a metal above hydrogen in the reactivity series?

Then hydrogen gas will be produced at the cathode

How to test if hydrogen gas is produced?

If the gas produced at the cathode burns with a squeaky pop with a lightened splint then there is hydrogen

How to test that oxygen gas is present?

If the anode relights a glowing splint dipped into the gas then there is oxygen

How to test that chlorine gas is produced?

If the gas produced at the anode turns damp blue litmus paper red and is then bleached white then the gas is chlorine