Name ____________________
Understanding the Balanced Chemical Equation
When ammonia gas decomposes it forms hydrogen gas and nitrogen gas. The balanced equation
for the reaction is
2NH3  2H2 + N2
1. Make drawings using circles that show the decomposition of 2 molecules of ammonia gas.
Reactants
Products
a. Does your drawing show conservation of atoms? How do you know?
2. Make drawings using circles that show the decomposition of 6 molecules of ammonia gas.
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a. Does your drawing show conservation of atoms? How do you know?
b. Are the ratio of ammonia molecules to hydrogen molecules the same as they are in the
first drawing? Show the ratios for both drawings.
c. Are the ratio of ammonia molecules to nitrogen molecules the same as they are in the
first drawing? Show the ratios for both drawings.
In the reverse direction, the reaction is a called the Haber process. The Haber process is an
important commercial process for making ammonia.
3. Make drawings using circles that show how 4 molecules of ammonia could be formed.
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Products
a. What type of reaction is this? How do you know?
4. Write a balanced equation for the formation of solid silver chloride from iron (II) chloride and
solid silver metal.
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a. Make drawings using circles that show the balanced chemical
equation.
Reactants
Products
b. What type of reaction is this? How do you know?
5. Write a balanced equation for the reaction of solid aluminum oxide into aluminum metal and
oxygen gas.
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a. Make drawings using circles that show the balanced chemical equation.
Reactants
Products
b. What type of reaction is this? Explain how you know.
6. Write a balanced equation for the reaction of gaseous methane with oxygen gas to for carbon
dioxide gas and water vapor.
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a. Make drawings using circles that show the balanced chemical equation.
Reactants
Products
b. Give the type of reaction and explain how you know.
7. Write a balanced equation for the reaction of lead (II) bromide and calcium phosphate to form
calcium bromide and lead (II) phosphate.
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a. Make drawings using circles that show the balanced chemical equation.
Reactants
Products
b. Give the type of reaction and explain how you know.
Summary: Explain why the number and kind of atoms must be the same before and after a
chemical reaction takes place.