8. Acids & Bases
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What is the number range of the pH scale?
1-14
What does the pH scale measure?
The acidity or alkalinity of a substance
What is the pH range for acids?
Less than 7
What is the pH range for alkalis?
Greater than 7
Name 3 indicators used in the lab
pH paper universal indicator red cabbage indicator
What is the pH value for neutral solutions?
7
What are produced when a metal reacts with an acid?
A salt and hydrogen
What is the test for hydrogen?
It burns with a pop
What is meant by neutralisation (S2)?
The pH value moves towards and reaches 7
How do you test for pH value?
• Add some suitable indicator to substance 2. Match colour to appropriate colour chart 3. Read off pH value matching that colour
Do strong acids have a higher or lower pH than weak acids?
Lower
Do strong alkalis have a higher or lower pH than weak alkalis?
Higher
What are the 3 acids used in the lab?
• Hydrochloric acid • Sulphuric acid • Nitric acid
What is the formula for hydrochloric acid?
H+ Cl- (aq)
What is the formula for sulphuric acid?
(H+)2 SO42- (aq)
What is the formula for nitric acid?
H+ NO3- (aq)
What is meant by neutralising an acid? (S3)
Getting rid of excess H+ (aq) ions
What is a base?
A substance that neutralises an acid by getting rid of excess H+ (aq) ions
Name the 4 types of base
• metals • metal oxides • metal carbonates • metal hydroxides
What type of salts are formed when sulphuric acid is neutralised?
sulphate salts
What type of salts are formed when nitric acid is neutralised?
nitrate salts
What type of salts are formed when hydrochloric acid is neutralised?
chloride salts
What is a salt? (S3)
When the H+ (aq) ions of an acid are replaced by metal ions
How do metals neutralise acids?
They lose electrons and force them onto H+ (aq) ions allowing them to form covalent bonds and produce molecules of H2 gas