Chemistry 2 Unit 5
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Chemistry 2 Unit 5
Salts and Electrolysis
What are the state symbols and what do they represent?
S = solid
l = liquid
g = gas
aq = aqueous solution
Whats the pH of Acids?
Strong acids = 0-3
Weak acids = 4-6
What's the pH of alkaline?
Weak alkaline = 8-11
Strong alkaline = 12-14
What are the products of reacting acids with metals?
What are the products of reacting acids with alkalines/ bases (metal oxides/hydroxides)?
What is the function of precipitation?
Precipitation is used to remove unwanted ions from solutions
How is ammonium salts produced and what are they used for?
Ammonium salts are produced by reacting ammonia with acids or dissolving in water.
Ammoni salts are used as fertilisers
What is electrolysis?
This is the process that issues electricity to breakdown compounds into elements
What occurs during electrolysis?
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
What is meant by reduction?
At the negatively charged electrode, positively charged ions gain electrons
What is meant by oxidation?
At the positively charged electrode, negatively charged ions lose electrons
What is the half equation of lead bromide?
: Pb2+ ➕ 2e- ➡ Pb
: 2Br- ➡ Br2 ➕ 2e-
What must be done to aluminium oxide before it can be electrolysed?
Aluminium oxide must be purified and melted to be electrolysed
How is aluminium extracted from aluminium oxide?
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
What is the equation for the electrolysis of aluminium oxide?
Aluminium oxide ➡ aluminium + oxygen
What is the half equation of aluminium oxide?
: Al3+ ➕ 3e- ➡ Al
: 2O2- ➡ 2O2 ➕ 4e-
Why's is carbon dioxide produced in the electrolysis of aluminium oxide?
The positive electrode is made of carbon, which reacts with the oxygen to produce carbon dioxide
Why is cryolite used?
Cryolite is used to lower the operating temperature of the electrolysis cell to enable the electrolysis of aluminium oxide
To save energy
What is brine?
Brine is a solution of sodium chloride in water
What does the electrolysis of brine produce?
The electrolysis of brine produces hydrogen and chlorine
Sodium hydroxide solution is also produced
What is the half equation of brine?
: 2Cl- ➡ Cl2 ➕ 2e-
: 2H+ ➕ 2e- ➡ H2
What can sodium hydroxide be used for?
Soap, bleach, neutralising acids
What is electroplating used for?
Make objects look more attracting
Protect metal objects from corroding
Increase hardness of surface
Reduce costs by using thin layers that pure metal