Salts and electrolysis

Question 1

How can you make soluble salts?

Answer 1

• Can be made from a metal or insoluble base plus the right acid
  1. Add the metal or insoluble base to the acid. The acid had been neutralised when excess solid sinks to the bottom
  2. Filter out excess solid so you are left with salt solution
  3. Evaporate the water to make the solution concentrated and leave behind solid salt crystals

Question 2

How can you make insoluble salts?

Answer 2

• Can be made with precipitation reactions
  1. Pick two solutions containing the ions you need and mix them
  2. Once the precipitation has settled at the bottom of the flask, filter it from the solution, wash it, and leave it to dry

Question 3

How do you make the fertiliser ammonium nitrate?

Answer 3

• Ammonia dissolves in water to make an alkaline solution. It can be neutralised with nitric acid to make the fertiliser ammonium nitrate
• Ammonium hydroxide + nitric acid = ammonium nitrate + water

Question 4

What is electrolysis?

Answer 4

The splitting apart of compounds with electricity

Question 5

What is electrolysis used for?

Answer 5

Used to recycle, purify and extract metals

Question 6

When can’t electrolysis occur?

Answer 6

Can’t happen unless the compound is melted or in solution because the ions have to be able to move

Question 7

What is OILRIG?

Answer 7

Oxidation Is Loss Reduction Is Gain

Question 8

How does electrolysis work?

Answer 8

• Electrons are taken away at the anode by the power pack and taken to the cathode
• At the anode, electrons are lost and the atom becomes an ion
• The ions move towards the cathode as opposite charges attract
• At the cathode, electrons are gained and the ion becomes an electron

Question 9

Why do the ions dissolve quickly during electrolysis?

Answer 9

Charged ions are very soluble

Question 10

Why might not all of the weight be transferred in electrolysis?

Answer 10

Some is lost as dirt at the bottom and some ions are still dissolved in the solution

Question 11

What happens during electrolysis of lead bromide?

Answer 11

-Molten lead bromide conducts electricity
-At the cathode, a lead ion accepts two electrons to become a lead atom
Pb2 + 2e- Pb
-At the anode, two bromine ions lose an electron each and become a bromine molecule
2Br- + 2e- Br2

Question 12

What happens when a salt is dissolved in water for electrolysis?

Answer 12

• If a salt dissolves in water there are H+ and OH- ions
• If a metal is more reactive than hydrogen, it stays in the solutions. If it is less, the metal is produced
• If a halide is present, that will be formed. If not, oxygen is

Question 13

What are the useful byproducts of electrolysis of sodium chloride?

Answer 13

-The chlorine is used in bleach and plastic, hydrogen is used in fuel cells and margarine, and sodium hydroxide is used in cleaning products