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Ask a Teacher - Chemistry - Formulae and Equations - A Question from Nathan
Student Name
Nathan
Question
I have many difficulties when it comes to doing ionic equations.
Have you got any tips for me that will help me to understand these
hard equations?
Answer
Equations are simply formulae replacing words so its
likely to be writing formulae which is causing you problems. This
is too big an area to go into in detail but there are a number of
basic rules that you must know. These are best illustrated in an
example:-
Magnesium chloride
Magneesium is
a metal soits ion must have a + charge. It has a valency of 2 so
the ion has a 2+ charge.
The chloride
ion must have a charge. Chlorine has a valency of 1 so the
chloride ion has a 1- charge.
The ions attract
each other in a ratio which results in the + and charges
balancing.
In this case it must be in the ratio of one Mg2+ to two
Cl-ie Mg2+ Cl-Cl- ie
Mg2+Cl-2
A shorter way
of doing this is to remember that the valency of the positive ion
tells you how many negative ions there must be and vice versa.
For more details
and examples see Standard Chemistry by Dickson and Wilson p.85-90.
