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One way to balance chemical equations is by trial and error. This is where you try using different coefficients until the numbers work out. This approach is also known as the inspection method. The inspection method works fine for many reactions, however, a more structured approach is needed for reactions that involve a number of reactants and products. We’ll develop it in the next few pages. 
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Single molecules in a chemical equation do not show a coefficient of 1. For example, O2 in a chemical equation means 1 molecule of oxygen.
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The coefficient in front of a substance applies to all atoms in the molecule. For example, 2CO2 means there are two carbon dioxide molecules. Each carbon dioxide molecule has two oxygen atoms, so the total number of oxygen atoms is four.
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Start by balancing only one element at first, then balance the next element, and so on, one element at a time. Every time you change a coefficient, go back and check the all elements you already balanced to make sure you have not unbalanced any of them.
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It is always easiest to balance pure elements last. Adding a coefficient to O2 will change only the number of oxygen atoms. But adding a coefficient to a compound like H2O will change both the number of hydrogen atoms and the number of oxygen atoms.
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| Glucose biomass can decompose to ethanol and carbon dioxide: C6H12O6 → C2H6O + CO2. What is the balanced reaction?
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| Asked |
Find the coefficients in order to balance the chemical equation. |
| Given |
The unbalanced chemical equation, C6H12O6 →C2H6O + CO2 |
| Relationships |
The same number of each type of atom must appear on each side. |
| Solve |
All atoms involved in the reaction are unbalanced.
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| Answer |
The balanced equation is C6H12O6 → 2C2H6O + 2CO2 |
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Balance the following reaction. Fe + Ca(NO2)2 → Fe(NO2)3 + Ca
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2Fe + 3Ca(NO2)2 → 2Fe(NO2)3 + 3Ca
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