WORKSHEET
BALANCING CHEMICAL EQUATION
Group/Class
Name
:
:
1.
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2.
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3.
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4.
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5.
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6.
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Goals:
1.
Students can count the number of atoms of reactans and products.
2.
Students can balance coefficient of chemical equation both the reactans and products.
Procedure:
1.
Write down the identities of the group members in the space available.
2.
Read the instructions on the worksheet and the questions as well.
3.
Observe the informations from the picture and power point by the teacher.
4.
After you observed the picture and power point, answer these questions on the worksheet by discussing them with the members of your group.

Question 1
1.
Look at the picture below.
2.
Count the number of each molecule.
Reactan
…
…
…
No. The number of atom
1 C
2 O
3 H
Question 2
Write down the balanced chemical equation of:
Zn(s) + HCl(aq)

ZnCl
2
(aq) + H
2
(g)
Steps:
Step 1
Product
…
…
…
Write down the chemical formulas of reactants and products. Include the phases/states.
Zn(s) + HCl(aq)  ZnCl
2
(aq) + H
2
(g)
Step 2
Add coefficients, so that the number of atoms of each element on the left side and on the right side is the same.

Pick the substance with the most complex chemical formula and set the coefficient as 1. Add temporary coefficients for other substances with letter a, b, c, d, etc.
a Zn(s) + b HCl(aq)

1 ZnCl
2
(aq) + c H
2
(g)

Balance the atoms of the most complex substance. If there are identical polyatomic ions on the left and the right sides, then balance them as polyatomic ions, not as atoms.
Atom
Zn
Cl
Number of the left side a b
Then,
1 Zn(s) + 2 HCl(aq)

1 ZnCl
2
(aq) + c H
2
(g)
Number of the right side
1
2
Result a= b=
1
2


Balance the other atoms
The remaining atom to be balanced is H atom.
Atom Number of the left side
2
Number of the right side
2c H
Then,
1 Zn(s) + 2 HCl(aq)

1 ZnCl
2
(aq) + 1 H
2
(g)

Make sure that every coefficient is a simple whole number.
Note: coefficient 1 is not written down in the equation.
Zn(s) + 2 HCl(aq)

ZnCl
2
(aq) + H
2
(g) ( BALANCED)
Balance the chemical equation below using the steps above.
1.
Al(s) + HCl(aq)

AlCl
3
(aq) + H
2
(g)
Result c= 1
Result:
… Al + … HCl 
… AlCl
3
+ … H
2

2.
NaOH(aq) + H
3
PO
4
(aq)

Na
3
PO
4
(aq) + H
2
O(l)
Result:
… NaOH(aq) + … H
3
PO
4
(aq)

… Na
3
PO
4
(aq) + … H
2
O(l)
3.
C
4
H
10
(l) + O
2
(g)

CO
2
(g) + H
2
O(g)
Result:
… C
4
H
10
(l) + … O
2
(g)

… CO
2
(g) + … H
2
O(g)

4.
AlCl
3
(aq) + H
2
SO
4
(aq)

Al
2
(SO
4
)
3
(aq) + HCl(aq)
Result:
… AlCl
3
(aq) + … H
2
SO
4
(aq)

… Al
2
(SO
4
)
3
(aq) + … HCl(aq)
Conclusion
Based on the discussion, take conclusion of the lesson today!