Chemistry 2 Unit 5

• S = solid
• l = liquid
• g = gas
• aq = aqueous solution

• Strong acids = 0-3
• Weak acids = 4-6

• Weak alkaline = 8-11
• Strong alkaline = 12-14

Acid➕metal➡salt➕hydrogen

Acid➕base/alkaline➡salt➕water

Precipitation is used to remove unwanted ions from solutions

• Ammonium salts are produced by reacting ammonia with acids or dissolving in water.
• Ammoni salts are used as fertilisers

This is the process that issues electricity to breakdown compounds into elements

During electrolysis the positively charged ions move to the negative electrode forming metals or hydrogen and the negatively charged ions move to the positive electrodes forming non-metals

At the negatively charged electrode, positively charged ions gain electrons

At the positively charged electrode, negatively charged ions lose electrons

• Neg: Pb2+ ➕ 2e- ➡ Pb
• Pos: 2Br- ➡ Br2 ➕ 2e-

Aluminium oxide must be purified and melted to be electrolysed

• Aluminium is obtained from aluminium oxide by electrolysis
• Aluminium ions are reduced to aluminium atoms at the negative electrode by gaining electrons
• Oxygen ions are oxidised to oxygen atoms at the positive electrode by losing electrons

Aluminium oxide ➡ aluminium + oxygen

• Neg: Al3+ ➕ 3e- ➡ Al
• Pos: 2O2- ➡ 2O2 ➕ 4e-

The positive electrode is made of carbon, which reacts with the oxygen to produce carbon dioxide

• Cryolite is used to lower the operating temperature of the electrolysis cell to enable the electrolysis of aluminium oxide
• To save energy

Brine is a solution of sodium chloride in water

• The electrolysis of brine produces hydrogen and chlorine
• Sodium hydroxide solution is also produced

• Neg: 2Cl- ➡ Cl2 ➕ 2e-
• Pos: 2H+ ➕ 2e- ➡ H2

Soap, bleach, neutralising acids

• Make objects look more attracting
• Protect metal objects from corroding
• Increase hardness of surface
• Reduce costs by using thin layers that pure metal