ELEMENTS IN SINGLE PLACE ON EACH SIDE
Balancing chemical equations where each element in the equation
occurs in only one chemical on each side is relatively easy.
Please look for this before you begin to balance an equation. The elements
that occur in only one place on each side should be balanced first.
It is also very helpful to see if an element occurs by itself such as
Cu and N2 in the equation to follow.
We study the case:
CuO + NH3 => Cu + H2O + N2
Each element occurs in one chemical on each side. For example, H only occurs
in NH3 on the left side and H2O on the right side. Cu only occurs in CuO
on the left side and Cu on the right side. Since Cu and N occur by
themselves on the right side this can be very helpful as we shall see.
If we entered this equation into Chem Spread, we would see this:
The program displays a spread sheet showing how each element is balanced.
Again you may ignore the row labeled e-. It shows N and H are not
balanced. N is to be balanced last because it occurs by itself on the
right side. We will discuss later why this is true.
H can be balanced by cross multiplication.
Thus we insert the
coefficient 2 in front of NH3 by clicking on the window and moving the
blinking cursor with the arrow keys. We insert the coefficient 3 in front
of H2O by doing the same thing.
We make the formula look like:
CuO + 2NH3 => Cu + 3H2O + N2 ? and hit the SUBMIT button.
Now O is unbalanced. We multiply CuO by 3 on the left side so that
there are 3 O's on each side:
3CuO + 2NH3 => Cu + 3H2O + N2 ? and hit SUBMIT.
Finally Cu is unbalanced. We multiply Cu by 3 on the right side so that
there are 3 Cu's on each side.
3CuO + 2NH3 => 3Cu + 3H2O + N2 ? and hit SUBMIT.
We see that all the elements are balanced and thus the equation is balanced.
Please note that when you have elements all by themselves such as
Cu and N2 in the above formula, you should balance them last because you
can always bring them into balance on the last few steps. N2 did not need
balancing but Cu was simple to balance because choosing it's coefficient
did not affect any other element in balance. That line of reasoning
will become clearer with practice.
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