Chemistry yr10 mock - Chapter 4 - making salts/electrolysis

What are salts made up of

A metal ion combined with the ion left over from the acid when the H+ ions react

Stage 1 of making salts that are soluble in water:

React the acid with an insoluble substance, like a metal carbonate, to produce the desired salt

Add this substance until it is in excess & no longer reacts

Potentially heat acid

Stage 2 of making salts that are soluble in water:

Filter off the left over metal using filtration

Stage 3 of making salts that are soluble in water:

Gently heat solution to evaporate some water/make more concentrated

Leave solution to cool down

Filter off the crystals off the salt

Allow crystals to dry

What is an electrolyte

Liquid/solution that conducts electricity

Give two types of substances that can be electrolytes

Molten ionic compound or aqueous solutions

Why can electrolytes conduct electricity?

They contain ions that are free to move

What process happens to the ions at the electrodes

Discharged

What equations are written for the reactions occurring at the electrodes

Half equations

Meaning of discharged;

Loss or gain of electrons, becoming electrically neutral

Give two times when electrolysis is used to extract metals

-Metal is more reactive than carbon

-If the metal reacts with carbon

Give 2 disadvantages of using electrolysis to extract metals

Lots of energy required to;

-Melt ionic compound

-Produce electrical current

From which molten mixture is aluminium extracted from

Aluminium oxide and cryolite

What material is the anode made form

Carbon, in the form of graphite

During aluminium extraction, why is the aluminium oxide mixed with cryolite?

-Lower the melting point

-Reduce amount of energy needed to melt it

Why must the anode be replaced alot

Carbon of the anode reacts with the oxygen produced to form carbon dioxide gas

In electrolysis of ionic solutions, what does the type of ion discharged depend upon

Ions of less reactive elements are discharged

What substance is produced at the cathode during aqueous electrolysis

Hydrogen, unless the metal is less reactive than hydrogen

What substance is produced at the anode during aqueous electrolysis

Oxygen, unless the solution contains halide ions

What happens to water molecules in aqueous solutions during electrolysis

They break down producing hydrogen and hydroxide ions

How is hydrogen produced at the cathode

Discharge of H+ ions

How is oxygen formed at the anode

Discharge of OH- ions

What reaction occurs at the cathode

Reduction

What reaction occurs at the anode

Oxidation

Half equation to show the discharge of hydrogen ions

"2H+ + 2e- → H2

Half equation to show the discharge of hydroxide ions

4OH- → 4e- + O2 + 2H2O