Balancing chemical equations?

Question

I really don't understand them! We just started to learn them in my 7th grade Science class. It's confusing with all the numbers. Anyone can sort of explain it to me?

Answer 1

When you show how chemicals react you have to make sure that you account for all of the atoms you started with and make sure you start with all of the atoms needed to make the compounds. The best way to begin to balance equations is to make a list of the reactant elements and the product elements and how many atoms of each you have to start with. Then you change the quantities by adding COEFFICIENTS in front of the compounds to balance.

example:

H2 + O2 = H20

reactants products
H = 2 ..... H = 2
O = 2 ..... O = 1 (not balanced)

You need two oxygen atoms on the product side, so put a 2 in front of the H2O. This will give you 2 oxygen and they will be balanced. Now we have:

H2 + O2 = 2H20

reactants products
H = 2 ..... H = 4
O = 2..... O = 4

Oops; when we put that "2" in , we changed the number of hydrogen atoms on the right side. Now we have to go back to the left side and balance the hydrogen by putting a 2 in front of the H2 (multiply coefficients x subscripts). Now we have:

2H2 + O2 = 2H2O

reactants products
H = 4 ..... H = 4
O = 2 ..... O = 2

The equation is now balanced; each element has the same number of atoms on both sides of the equation.

Answer 2

In order to balance an equation, each side of the arrow has to have the same number of elements. Let me give you an example:

Let's say you have this equation -
2 Oxygens + 3 Golds --> 1 Oxygen + 3 Golds

Now if you look closely, there are more Oxygens on the right side than the left. So you need to make both sides equal. All you have to do is simply change the 1 Oxygen to 2 Oxygens. So your new, finished equation would look like this:

2 Oxygens + 3 Golds --> 2 Oxygens + 3 Golds

That's a very simple equation, but if you had subscripts, it would follow the same rule: Always make sure both sides of the arrow have EQUAL numbers of each element!

I hope this helped you. I know it's tough, but don't give up!

PS - remember to never change the subscripts! To balance, just put extra numbers in FRONT of the element symbol. The subscripts never change! Only the number of elements changes.

Answer 3

Balancing chemical equations isn't the easiest thing in the world to explain in a written answer, but I'll give it a shot. In all the examples, a number after a chemical symbol will be a subscript, since I can't write them any other way.

Here's the one most important thing to remember: make sure you have the same amount of each element on both sides.

Let's start with something easy: oxygen and hydrogen gas reacting to form water.

The unbalanced equation is:

H2 + O2 >>> H2O

If you look at the equation and make a tally of how many atoms there are of each element, you'll realize why the equation isn't balanced.

Hydrogen: 2 on the left side
2 on the right side

Oxygen: 2 on the left side
Only 1 on the right side

The way you get the number of atoms of each element is by using the subsricpts--the little numbers below and after each element. On the left side, hydrogen has a 2 after it so we know there are 2 atoms of hydrogen. On the right side, the H also has a 2 after it, so we know that there are 2 atoms of hydrogen there as well. The hydrogen balances. The oxygen, on the other hand, does not. There's a 2 after it on the left side, but there isn't a subsricpt with it on the right side, which means that there is only one atom of oxygen. That's where our problem comes in: you can't make an atom of oxygen disappear; if you start with 2, you need to finish with 2. That's when you use coefficients--the big numbers before each element or compound formula. Now, let's try to balance the equation using some coefficients.

What we need is 2 oxygen atoms on the right side to balance the equation, so if we put a coefficient of 2 in front of the water (H2O) on the right side, then the 2 will be multiplied to both the oxygen and the hydrogen.

H2 + O2 >>> 2H2O

Now, let's recount our atoms to make sure we balanced out.

Hydrogen: 2 on the left side
Uh-oh. . .4 on the right side!

Well, it didn't balance out the first time, because the coefficient 2 multiplies to the subscript of 2 that the hydrogen has. It's kind of like distributing in math, but it isn't going to make the problem all that much harder.

If we put a coefficient 2 in front of the hydrogen on the left side. . .

2H2 + O2 >>> 2H2O

Let's count up our atoms again.

Hydrogen: 4 atoms on the left side (coefficient 2 x subsricpt 2)
4 atoms on the right side (coefficient 2 x subsricpt 2)

Oxygen: 2 atoms on the left side (subscript 2)
2 atoms on the right side (coefficient 2)

OK. We've got the same amount of atoms of each element on both sides, so the equation balances. Let's try another one.

This time, we'll do aluminum and oxygen combining to form aluminum oxide.

The unbalanced equation is this:

Al + O2 >>> Al2O3

Let's tally up the atoms we have of each element again.

Aluminum: 1 atom on the left side (no subscript means 1)
2 atoms on the right side (subsript 2)

Oxygen: 2 atoms on the left side (subscript 2)
3 atoms on the right side (subscript 3)

It's pretty obvious that the equation isn't balanced, so we're going to have to use coefficients again. Let's try to get the oxygen to balance out first.

If we put a coefficient of 2 in front of the Al2O3, then that will give us 6 oxygen atoms (coefficient 2 x subscript 3 = 6 atoms).

Al + O2 >>> 2Al2O3

We can put a coefficient 3 in front of the O2 on the left side, and that'll give us 6 atoms of oxygen on both sides. (coefficient 3 x subscript 2 = 6 atoms).

Al + 3O2 >>> 2Al2O3

Let's tally up our atoms again.

Aluminum: 1 atom on the left side
4 atoms on the right side (coefficient 2 x subscript 2 = 4 atoms)

OK, so our aluminum doesn't balance, but we can fix that easily with just one coefficient in front of the aluminum on the left side. If we need 4 atoms to balance, can you guess what the coefficient will be?

If you said "4," you would've been right. Our final equation would look like this.

4Al + 3O2 >>> 2Al2O3

I realize this probably isn't as good as you'd like, but I hope it helps to some extent. Good luck with it!

Answer 4

First, write the chemical equation. Then, make a table with all the elements on the left hand side (LHS) and right hand side (RHS) of the equation. Try to balance out the numbers...and voila!

Example Table:
Element LHS RHS
O
H
Ca

Answer 5

yea well when u are balancing them you are not alllowed to change the subscripts (small number under the chemical symbol) you can only change the coeficiants (number to the left of the chemical symbol) your object is to get the same amount of each chemical in each equation.
and example
2ag(2 subscript)au(3 subscript)
thi means there are 4 ag's and 6 au's
so in the next equation must have the same amount

Answer 6

use your engine search and type: balancing chemical equations,, you should get an example, that will help you understand the movement of atoms and electrons, everything in the world should be balanced.

Answer 7

i know how to balance equations but i also dont know how to explain it over this.... it might help if you say what you DO understand about them and then someone can take it from there!

Answer 8

I know how to balance them, but I see no possible way I can explain how to do so over a message (as you said, it's confusing). I just thought I'd get you nowhere and let you know.