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# Balancing Chemical Equations

## Using coefficients so the same number of each atom occurs in both reactants and products of a chemical equation.

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Practice Balancing Chemical Equations

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Bring Back the Shine

### Bring Back the Shine

Credit: Vassil
Source: http://commons.wikimedia.org/wiki/File:Bijou_Miao.jpg

This unusual piece of jewelry is made of silver. Do you see the black smudges here and there on the surface of the silver? That’s tarnish.

#### News You Can Use

• Silver is a metal that tarnishes easily. It happens in a chemical reaction. A compound called silver sulfide forms on the surface of the metal.
• Credit: Mauro Cateb
Source: http://www.flickr.com/photos/mauroescritor/8061291318/

Untarnished silver is quite beautiful [Figure2]

• Fortunately, a different chemical reaction can be used to remove the tarnish. The reaction involves another metal replacing silver in the silver sulfide. This type of reaction is called a replacement reaction.
• Watch this short video to see how easy it is to remove tarnish from silver:

#### Can You Apply It?

1. How does silver tarnish?
2. Describe the aluminum foil method of removing tarnish from silver.
3. Describe in words the chemical reaction that takes place in question 2. Write a balanced chemical equation for this reaction. How can you tell that the equation is balanced?
4. The reaction in question 3 is a replacement reaction. What rules determine whether one element will replace another in a chemical compound?
5. Can copper (Cu) replace silver (Ag) in silver sulfide (Ag2S)? Why or why not?
6. Name three other metals that could replace silver in chemical compounds. Name one metal that could not replace silver.

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