Download WRITING CHEMICAL EQUATIONS

WRITING CHEMICAL EQUATIONS
REVIEW:
1.
Evidence of a chemical reaction includes:
4.
2.
5.
3.
The Law of Conservation of Mass/Matter states:
BASICS ABOUT WRITING EQUATIONS:
Chemical formulas (of elements, covalent compounds, acids, ionic compounds, bases, etc.) show
chemistry at a standstill. Chemical equations show chemistry in action.
The general formula for a chemical equation is:
There may be one or more reactants and one or more products.
Equations always tell us 3 things:
1.
2.
3.
Two important principles to remember:
1. Every chemical compound has a formula which cannot be altered. If the formula is
altered, you now have a new chemical with a new chemical composition and new
chemical and physical properties.
2. A chemical reaction must account for every atom that is used. No atom can ever go
unaccounted for in a chemical equation. What law is this an application of?
SPECIFICS ABOUT WRITING CHEMICAL EQUATIONS:
1. There are seven elements that are diatomic when they stand alone. Always include the
subscript 2 when they are by themselves. They are:
Also, sulfur can naturally exist as
and phosphorous can naturally exist as
2.
means “yields” or “produces” or “forms” and shows the direction of the reaction.
It means that the reaction goes to completion, or until the reactants are used up.
3.
or
or
shows that the reaction is reversible and can proceed in
either direction until it reaches equilibrium. Both reactants and products are present at all
times once the reaction has begun.
4.
or
above the arrow shows that heat has been added.
5. A chemical written above the arrow shows that it is a
the reaction, but isn’t produced or consumed.
6.
. It speeds up
is placed between all formulas on each side of the arrow.
7. These symbols written as subscripts following the formulas mean:
(s)
(l)
(g)
(aq)
BALANCING CHEMICAL EQUATIONS:
1. Before beginning to balance an equation, check each
to ensure that
it is correct.
can NOT be altered IN ANY WAY once you
begin balancing an equation.
2. The law of
states the same
number of each atom must appear on the left and right sides of the chemical
equation. Otherwise, atoms would be gained or lost (i.e. created or destroyed, and
not simply transferred).
3. Balancing is done by placing
in front of the formulas to
ensure the same number of atoms of each element on both sides of the arrow. For
now, the
will always be whole numbers.
4. Treat chemistry coefficients just like coefficients in algebra. Treat the
= sign in algebra.
as an
5. Balance either the most obscure elements first or the ones that appear only once
on each side of the equation. Always balance the elements
and
last.
6. If
group.
ions appear on both sides of an equation, keep them as a
7. If you get stuck,
type of atom.
all coefficients and start over with a
8. If you still get stuck, try
coefficients already entered.
9. Once balanced, you must do three things:
1.
2.
3.
or
all the