The pH scale
measures how
acidic or
alkaline a
substance it is.
A pH of 7 is neutral
A pH greater than 7 are alkaline (basic)
Alkalis are bases that are soluble in water.
All alkalis are bases but not all bases are alkalis.
The higher the pH, the stronger the alkaline
A pH lower than 7 are acidic
The lower the pH, the stronger the acid
If a universal
indicator is added
to the solution, it
changes colour to
show the pH of the
solution.
Bases and Alkalis
A base is a substance that neutralises an acid
Bases such as metal oxides and metal hydroxides react with acids to form neutral products
Examples of bases:
Copper Oxide
Zinc Hydroxide
Bases that are also soluble in water are called alkalis
Examples of alkalis:
Sodium Hydroxide
Potassium Hydroxide
All alkalis are bases
Alkali + Acid = pH of mixture rises
the alkali reacts with it forming neutral products
Acid + Alkali = the pH to fall
the alkali is removed by the reaction with the acid
when acidity or alkalinity is removed it is called NEUTRALISATION
a neutralisation always produces salt and water (nothing else)
Acid + base = salt + water
If the acid is hydrochloric acid,
the salt will be a chloride
Acid: hydrochloric acid
+ Base: copper oxide
= Salt+Water: copper chloride+ water
If the acid is nitric acid,
the salt will be a nitrate
Acid: nitric acid
+ Base: calcium hydroxide
= Salt+water: calcium nitrate + water
If the acid is sulfuric acid,
the salt will be a sulfate
Acid: sulfuric acid
+ Base: sodium hydroxide
= Salt+water: sodium sulfate + water
Sufuric acid is used to
clean metal surfaces
before they're painted.
It's also an important
starting material in the
production of fertilisers
and is used in car
batteries.