How to Write Chemical Equations
Mr. Causey shows you how to WRITE chemical equations. Mr. Causey discusses the parts of a chemical equation, the symbols involved and the steps required.
WARNING: It is important that you ALREADY know how to name and write chemical formulas and can recognize the different types of chemical reactions.
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Polyatomic Ion Cheat Sheet:
Writing and Balancing:
A chemical equation is a symbolic representation of a chemical reaction and it reveals three things; the reactants, the products, and the mole ratios, or the amounts. And learning to write a proper chemical equation is the key to good stoichiometry.
Now, in order to write proper chemical equations we need to know a few symbols.
“g” is for gas
“l” is for liquid
“s” stands for solid and
“aq” is for aqueous
Aqueous just means dissolved in water. It’s important that we understand and use these symbols to tell which state or form the different elements or compounds are in.
An arrow is used for yield or produces; the capital Greek letter delta stands for change; the plus sign means combine; and we use an up arrow to show that a gas has been released into the atmosphere. Make sure you copy down and learn these symbols. We are going to use them a lot.
Okay, let’s look at the steps for writing equations.
First, identify the reactants and products. If you don’t know how to read chemical names or write formulas, you need to go my channel and watch those lessons. It is imperative that you know how to identify reactants and products. Second, write formulas for everything, both the reactants and the products. Third, place the reactants on the left separated by a plus sign; place the products on the right separated by a plus sign; and put an arrow in the middle. It’s pretty much that easy.
If you can read chemical names, write chemical formulas and follow these simple steps you are home free.
Now, let’s look at an example.
Aluminum reacts with phosphoric acid to yield hydrogen gas and aluminum phosphate. Now watch this very carefully, and if you need to stop, rewind and watch it again. That’s the beauty of video. We have the technology.
First, identify the reactants. Second, identify the products. Then, write the formulas. There we go. Viola!
Practice time! Let’s put what we have learned to good use. Let’s see how well do.
Aluminum and oxygen combine to form aluminum oxide. First, find and write the reactants. Second, find and write the products. Then write the equation using the proper symbols. For right now, don’t worry about balancing the equation. The important thing here is to write a good chemical equation.
Next, dinitrogen pentoxide reacts with water to produce nitric acid. First, find and write the reactants. Notice the reactants are dinitrogen pentoxide and water. Second, find and write the products. Then write the equation.
Sodium bicarbonate produces sodium carbonate, water, and carbon dioxide. First, find and write the reactants, or in this case the reactant. Second, find and write the products. Did you get all three? Notice that this was a decomposition reaction.
Let’s recap: You learned the description of a chemical equation; you learned the symbols for writing chemical equations and you learned how to write chemical equations.