When you see the name "chemical equations," the word "equation" makes us think of math equations. There is some similarity. Like all equations, something has to be "equal."
In a math equation the value of the left side of the equal sign is the same value as the right side. These values also exist at the same time like a balance.
In a chemical equation the atoms on the left side have to be equal to the atoms on the right side of the arrow, but they don't exist at the same time. The chemical equation represents movement. For example, here we start with carbonic acid consisting of 2 hydrogen atoms, 1 carbon atom, and 3 oxygen atoms. The atoms rearrange and become water and carbon dioxide. All original atoms are still accounted for.
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Atoms combine in simple ratios. That means the chemical equations that show and balance the starting "reactants" and ending "products" are fairly simple. Unlike math equations, chemical equations are showing a progression of time.
Here we see how hydrogen and oxygen (reactants) react and produce water. It's a simple rearrangement.
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Bike Example for Balancing Chemical Equations:
We are all familiar with bicycles, tricycles, etc. It's also easy to see how many wheels are necessary to build them. Because this is very visual (and atoms are too small) I'm going to use the manufacturing of these products as an introduction to balancing chemical equations.
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This company is going to promote their super durable tires. The tires will be the biggest expense in making these cycles. Because of that, the company may recall cycles that aren't selling and put the wheels on the cycles that are selling.
Notice that the wheels are only sold to the manufacturer in pairs.
Source: http://www.chemistryland.com/StatusPages/Student_Status_130pc.html
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The company that produces these pedal cars can use abbreviations similar to the way chemistry uses abbreviations. For example Cb can represent the "Car body". "W" will represent the "wheels." Remember that the wheels are only purchased in pairs. So "W2" repesents a pair of wheels. The production scheme is that one car body (Cb) is added to two pairs of wheels (2W2) to make a complete car (CbW4).
We know a car has four wheels, so the formula of CbW4 should seem logical.
The approach in balancing chemistry equations uses the same logic.
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The carbon "C" is like the car body. Chlorine always comes as a pair, so it's like the wheels that come in pairs. To make carbon tetrachloride we need carbon and chlorine.
C + Cl2 ­> CCl4
This is the unbalanced chemical equation because the number of chlorine atoms in the product is different than what we started with. We are 2 chlorine atoms short, so we show two pairs of chlorines.
C + 2Cl2 ­> CCl4
This is the balanced chemical equation.
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When we manufacture tricycles, we run into a problem. We know we need to add wheels (W2) to a trike body (Tb). This gives us the unbalanced equation:
Tb + W2 ­> TbW2
As you can see this number of wheels don't match. If we use two pairs of wheels (2W2), we end up with an extra wheel. So we compensate by starting with two trike bodies. Then we are short wheels, so we go with 3 pairs. At this point we the number of trike bodies and wheels we start with match what we end with; so it's now a balanced production equation.
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A trike body attaches to 3 wheels. Aluminum attaches to 3 chlorine atoms. Because of this similarity, the equation for making aluminum chloride has the same issues. We start with an unbalanced (skeleton) chemical equation.
Al + Cl2 ­> AlCl3 (short 1 chlorine at start)
Al + 2Cl2 ­> AlCl3 (ends up with extra chlorine)
2Al + 2Cl2 ­> 2AlCl3 (short 2 chlorines at start)
2Al + 3Cl2 ­> 2AlCl3 (all atoms match)
We see that starting with Cl2 is not enough chlorine atoms, so we go with 2Cl2 but then end up with an extra chlorine atom. So we go with 2 aluminum atoms, but then we are short 2 chlorine atoms. Finally, by going with 3 pairs of chorines atoms, we end up with a balanced equation.
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Looking at the unbalanced equation, we see that the number of wheels on the left side (4 wheels) are twice as many as those on the finished side (2 wheels). So we see that if we finished with 2 bicycles, we would use all 4 wheels. To finish with two bicycles we have to start with 2 bicycle bodies. Now we have a balanced equation.
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This is also a double­
replacement reaction.
Here the barium atom swaps places with the calcium atom. When that happens, we make barium sulfate which is given to patients to drink, so x­rays can see the stomach and intestines. 11
Coefficients are used to balance the equation.
For example... N2H4+O2 > N2+H2O Unbalanced or balanced?
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