hey it's professor Dave, let's learn how to balance equations
when substances
interact and chemistry occurs we can describe the process using something
called a
chemical equation. for example when sodium metal reacts with chlorine gas
you get sodium chloride or table salt. the arrow here
is what separates the reactants, the things that react
from the products, the things that you get. the arrow also shows the direction of the
reaction. when you see a chemical reaction
it describes the substances involved but if we want to be very accurate
we need to balance the equation so that there are the same
number of atoms on both sides because atoms won't just appear or disappear
they all have to be accounted for. for example in order to make one molecule
of sodium chloride
we need one sodium atom and one chlorine atom. but chlorine gas molecules
have two atoms of chlorine each so one molecule of chlorine gas
will react with two sodium atoms to give
two molecules of sodium chloride. we need to include coefficients before each
substance
to indicate how many of each we need to make the equation balanced.
let's make the distinction that these subscripts
tell us how many atoms of a given element are in
one molecule, whereas these coefficients
tell us how many of that molecule there are. in the reaction
where hydrogen gas and oxygen gas go to make water
we can see that the gases have two atoms each
and water has two hydrogen atoms and one oxygen atom
we will need to combine the substances in this ratio
to make this equation balanced. now there are the same number of hydrogen
and oxygen atoms on both sides of the equation
even though they have rearranged their combinations. so if we have an
unbalanced equation like this one that we need to balance there's an easy way
to do it.
we will balance things one element at a time. if an element exists by itself
do that one last. start with an element that is present in just one compound on
each side
let's do carbon first
on the left there are three carbon atoms for every molecule
of propane and on the right there is just one
for every molecule of carbon dioxide so according to the carbons we're going to
make three
CO2's with every propane. let's put a three there.
now the carbons are balanced, three carbon atoms
on each side. next let's do hydrogen. there's
eight on the left and two on the right, that means we will make four waters
with every propane. now hydrogen is balanced
eight on each side. last is oxygen. on the right
there's six from CO2 and four from water
for a total of 10, that means we will need five molecules of 02
to get 10 oxygen atoms on the left side. now the equation is balanced.
there is the same number of each type of atom on both sides
showing us the correct ratio in which these molecules will have to react.
these coefficients are going to be very important as we move forward
as we will have to be able to balance equations to make predictions about
chemistry
let's check comprehension
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