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CHEMICAL CHANGES KEY WORDS (pH SCALE: A scale from 0-14 for measuring…
CHEMICAL CHANGES KEY WORDS
OXIDATION:
Gain of oxygen
or a
loss of electron
s in the reaction
DISPLACEMENT REACTION:
Where a
more reactive metal
displaces
a less reactive metal from
its compound.
e.g -
zinc + copper sulfate > zinc sulfate + copper
REACTIVITY SERIES:
Metals in
order of their reactivity
based on their tendency to
form positive ions.
POTASSIUM
SODIUM
LITHIUM
CALCIUM
MAGNESIUM
CARBON
ZINC
IRON
HYDROGEN
COPPER
SILVER
GOLD
REDUCTION:
Loss of oxygen
or a
gain of electrons.
NEUTRALIZATION:
When an
acid is neutralized by an alkali, base
(a metal oxide) or a carbonate to produce
a salt.
Acid + metal oxide → salt + water
Acid + alkali → salt + water
Acid + carbonate → salt + water + carbon dioxide
ACID:
Produces H+ ions in aqueous solutions
pH SCALE:
A scale from 0-14 for measuring acidity and alkalinity. 0-6= acid,, 7= neutral,, 8-14= alkali.
The pH scale is
logarithmic
and as a result, each whole
pH value below 7 is ten times more acidic than the next higher value.
ALKALI:
Produces OH+ ions in aqueous solutions
IONIC EQUATIONS FOR NEUTRALIZATION:
H+(aq) + OH-(aq) → H2O(l)
TRITRATION:
A method for determining the
reacting volumes of acid and alkali solutions
by using a suitable
indicator
WEAK ACID:
An acid that is o
nly partially ionized in a aqueous solution
eg ethanoic cid, citric acid and carbonic acid.
STRONG ACID:
An acid that is
completely ionized in aqueous solutions
eg hydrochloric acid, nitric acid and sulphuric acid.
ELECTROLYSIS:
The separation of an
ionic compound
using electricity,
Ions are discharged at electrodes
(anode = positive, cathode = negative) producing elements.
When
negative non-metal ions
(anions) arrive at the
positive electrode
(the anode), they
lose electrons to form neutral atoms or molecules.
This is called
oxidation
. For example:
2Br- → Br2 + 2e-
When positive metal ions (cations) arrive at the
negative electrode (
the cathode), they
gain electrons to form neutral metal atoms.
This is called
reduction.
For example:
Pb2+ + 2e- → Pb
HALF EQUATIONS:
An equation for a reaction occurring at an electrode during electrolysis.
Cations go to the cathode. They need to gain enough electrons to make them neutral.
So an Al3+ ion needs to gain three electrons:
Al3+ + 3e- → Al
Half-equations for
non-metal anions
are more difficult to balance. For example, chloride ions make chlorine gas. Most non-
metal elements formed in electrolysis are diatomic molecules
(eg Cl2). For example:
Cl- → Cl2
Add in two electrons to balance the charge so that both sides have the same charge. The two electrons need to go on the right-hand side, so that both sides have an overall charge of -2. For example:
2Cl- → Cl2 + 2e
ELECTROLYTE:
Liquids and solutions that are able to
conduct electricity.
