The pH scale
Alkaline
•Hydrogen Ions make acidic
solutions
•Hydroxide ions make basic/alkaline
solutions.
Neutral
Acid
•Bases are substances that can
neutralise acids. They are usually
metal oxides or metal hydroxides.
•Alkalis are soluble bases
Neutralisation
H+ (aq) + OH-(aq) -> H2O (l)
• The acid reacts with the alkali to form a salt and water which is a
neutral solution. The hydrogen ions in the acid join with the
hydroxide ions in the alkali to form a neutral water molecule. The
gas in the acid reacts with the metal or ammonium in the alkali to
form an ionic salt.
• E.g.
Hydrochloric acid + sodium hydroxide -> sodium chloride +water
HCl(aq)
+ NaOH(aq)
->
NaCl(aq) + H20 (l)
Reactions of Salts
Acid + Metal -> a salt + hydrogen
E.g. Sulphuric acid + potassium -> potassium sulphate + hydrogen
This is a displacement reaction
Acid + Base -> a salt + water
E.g. Sulphuric acid + sodium oxide -> sodium sulphate + water
This is a Neutralisation reaction
Acid + Alkali -> a salt + water
E.g. Sulphuric acid + potassium hydroxide -> potassium sulphate + water
This is a neutralisation reaction
Acid + Carbonate -> a salt + water + carbon dioxide
E.g. Sulphuric acid + copper carbonate -> copper sulphate + water + carbon dioxide
Naming Salts
type of metal or ammonium
in the
base/alkali/metal/carbonate
which reacts with the acid
This comes from the acid
Sodium Chloride
Remember
•Hydrochloric acid makes chloride salts
•Sulphuric acid makes sulphates
•Nitric acid makes nitrates
Precipitation Reactions
• This is a reaction where a solid insoluble salt is produced when two
soluble salt solutions are mixed together. This type of reaction is
important when we want to remove heavy metal ions from polluted
water.
• E.g. Lead nitrate + Sodium chloride -> lead chloride + sodium nitrate
Pb(NO3)2(aq) +
2NaCl(aq)
-> PbCl2(s)
+ 2NaNO3(aq)
• E.g.
Silver nitrate + potassium iodide -> silver iodide + potassium nitrate
AgNO3(aq) +
KI2(aq)
-> AgI(s)
+ KNO3(aq)
Questions
1.
Name the salt which is produced when hydrochloric acid reacts
with ammonium hydroxide.
2.
Which ions make acidic solutions?
3.
What is an alkali?
4.
Write the balanced symbol equation for sulphuric acid +
potassium. Include the state symbols
5.
What is produced in a precipitation reaction?
6.
What is the equation for a neutralisation reaction?
Answers
1.
Ammonium Chloride
2.
Hydrogen Ions
3.
A soluble base
4.
H2SO4(aq) + K(s) -> KSO4(aq) + H2(g)_
5.
An insoluble salt
6.
H+ (aq) + OH-(aq) -> H2O (l)