balancing chemical equations
Explanation:
A chemical equation is a method of writing a chemical reaction, where the reactants are on the left and the products are on the right. A balanced chemical equation shows the number of each reactant that is needed and the number of products that are produced during a reaction.
Law of Conservation of Mass:
“In an ordinary chemical reaction, matter is neither created nor destroyed.”
When writing a chemical equation there should be the same number of atoms on the left side as there are on the right side.
2 H20 (l) → 2 H2 (g) + O2 (g)
The left side:
On the left side there are two H20 molecules, which is shown by the H20 having a coefficient of 2. One H20 molecule is composed of 2 hydrogen atoms and 1 oxygen atom. In total there are 4 hydrogen atoms and 2 oxygen atoms.
The right side:
There are two hydrogen molecules and one oxygen molecule. Each hydrogen molecule contains 2 hydrogen atoms. Each oxygen molecule contains 2 oxygen atoms. In total there are 4 hydrogen atoms and 2 oxygen atoms.
Walk through of a problem:
N2 (g) + H2 (g) → NH3 (g)
In most cases, it is better to balance the hydrogen and oxygen atoms last.
We will balance the nitrogen atoms fist. Because there are 2 nitrogen atoms on the left side and only 1 nitrogen atom on the right, we will give NH3 a coefficient of 2. This balances the amount of nitrogen on both sides.
N2 (g) + H2 (g) → 2 NH3 (g)
Now on the right side we have total of 6 hydrogen atoms. We will then give the hydrogen molecule a coefficient of 3 to balance out the number of hydrogen atoms on both sides.
N2 (g) + 3 H2 (g) → 2 NH3 (g)
Lowest whole-number ratio:
The chemical equation below, though the number of atoms on the left and right are balanced. This is still considered incorrect.
6 Na + 6 H20(l) → 6 NaOH(aq) + 3 H2(g)
By convention, the chemical equation shows the lowest whole-number ratio.
2 Na + 2 H20(l) → 2 NaOH (aq) + H2 (g)
Subscripts:
Subscripts are used to express the state of the substance or whether it is aqueous, meaning it is dissolved in water.
(l) Liquid
(g) Gas
(s) Solid
(aq) aqueous
work sheets with answers
http://science.widener.edu/svb/tutorial/rxnbalancingcsn7.html
http://tjca.teamcfa.org/uploads/1710/original/Balancing%20chemical%20equations%206.pdf
http://www.kentchemistry.com/Worksheets/Regents/Units/MathofChem/WSBalancing21.pdf
http://www.sciencegeek.net/Chemistry/taters/EquationBalancing.htm
http://wolgemuthe.psd401.net/chemistry/06%20-%20balancing/documents/Worksheet%20-%20Balancing%20Chemical%20Equations.pdf
http://tjca.teamcfa.org/uploads/1710/original/Balancing%20chemical%20equations%206.pdf
http://www.kentchemistry.com/Worksheets/Regents/Units/MathofChem/WSBalancing21.pdf
http://www.sciencegeek.net/Chemistry/taters/EquationBalancing.htm
http://wolgemuthe.psd401.net/chemistry/06%20-%20balancing/documents/Worksheet%20-%20Balancing%20Chemical%20Equations.pdf
more RESOURCES
Videos:
http://www.youtube.com/watch?v=RnGu3xO2h74
http://www.youtube.com/watch?v=UGf60kq_ZDI
http://www.youtube.com/watch?v=_B735turDoM
http://www.youtube.com/watch?v=YAutl-G7g4A
Other sites:
http://chemistry.about.com/cs/stoichiometry/a/aa042903a.htmhttp://www.dummies.com/how-to/content/how-to-balance-chemical-reactions-in-equations.html
http://chemistry.about.com/od/chemistryquickreview/a/balanceequation.htm
http://www.youtube.com/watch?v=RnGu3xO2h74
http://www.youtube.com/watch?v=UGf60kq_ZDI
http://www.youtube.com/watch?v=_B735turDoM
http://www.youtube.com/watch?v=YAutl-G7g4A
Other sites:
http://chemistry.about.com/cs/stoichiometry/a/aa042903a.htmhttp://www.dummies.com/how-to/content/how-to-balance-chemical-reactions-in-equations.html
http://chemistry.about.com/od/chemistryquickreview/a/balanceequation.htm