Balancing Chemical Equations

Multiple Choice

Why must a chemical equation need to be balanced?

• Law of Conservation of Matter

• Law of Conservation of Energy

• Law of Balancing Equations

• Law of Partial Pressure

Multiple Choice

Why must the subscripts not be changed when balancing a chemical equation?

• It changes the number of molecules in the reaction.

• It changes the type of chemical it is.

• It defies the Law of Conservation of Matter.

• It defies the Law of Conservation of Energy.

Fill in the Blanks

The

in front of the chemical formula can be changed when balancing a chemical equation. (Hint: Think about what you learned from PhET simulation.)

There are five steps for this method.
1) Create a table under the chemical equation.
a) Create a column under the yield arrow and write the symbol for
each element.
2) Draw a line under each plus sign.
3) Write the number of each type of type of element in the column formed
4) Choose one element to balance at a time.
a) Change the coefficient to the substance of the element you are
balancing.
b) Multiply the coefficient for every number in the column
5) Repeat step 4 until each element is balanced.
a) You may need to repeat this for an element more than once.

​A Method for Balancing Equations

The next several slides will show an example of how to use this method to balance.

There are two examples of how it can be used.

​A Method for Balancing Equations

Reorder

Reorder the following for the five steps for balancing a chemical equation.

• Create a column under the yield sign with the symbols for each element.

• Draw a line under each plus sign creating columns.

• Write the number for each element in the column.

• Choose one element at a time to balance.

• Change the coefficient of the substance and multiply each number of the column.

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

Multiple Choice

What can be changed to balance a chemical equation?

• coefficients

• subscripts

• types of atoms

• types of molecules

There is a special way that we can balance chemical equations when there are polyatomic ions that appear on both sides of the equation.

The next slides show how to deal with balancing chemical equations with polyatomic ions.

Balancing with Polyatomic Ions

Drag and Drop

Balancing chemical equation requires you to change the ​

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of the chemical. This is the number ​

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of the chemical formula. You can NEVER change the ​

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of the chemical formula. The chemical equation is balanced when both the reactants and the products have the ​

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number of each type of element. The ​polyatomic ions can be treated as ​

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item provided it shows up on both sides of the yield arrow.

Drag these tiles and drop them in the correct blank above

coefficients

in front

subscripts

equal

a single

separate

in back

different

Drag and Drop

When balancing a chemical equation you need to change the ​

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in the front of the chemical formula. You can never change the ​

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of the chemical formula. Polyatomic ions can be balanced as a ​

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item when it appears on both sides of the yield sign. A chemical equation is balanced when the number of atoms of each type of element is ​

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between the reactants and the products.

Drag these tiles and drop them in the correct blank above

coefficients

subscripts

single

equal

different

separate