Writing And Balancing Chemical Reactions, Stoichiometry, Limiting Reactants Worksheet With Answers - Chem110 Page 4
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8CHEM110 Week 5 Notes (Stoichiometry)
Page 4 of 8
To balance oxygen, recognize that the least-common multiple between a 2 and a 13 is 26.
To achieve this will require a 13 coefficient for oxygen and doubling the coefficients for
carbon dioxide and water. Additionally, the coefficient for butane needs to be doubled.
C
H
(g) + 13O
(g)
→
8CO
(g) + 10H
O(g)
4
10
2
2
2
__4__ C __8__
_10__ H _20__
_26__ O _26__
finally,
2C
H
(g) + 13O
(g) →
8CO
(g) + 10H
O(g)
4
10
2
2
2
__8__ C __8__
_20__ H _20__
_26__ O _26__
When balancing reactions with ionic compounds, it helps to balance polyatomic ions as a
group when they stay together on the left and right sides of a chemical reaction.
Na
CO
(aq) + CaCl
(aq)
→
CaCO
(s) + NaCl(aq)
2
3
2
3
__2__ Na __1__
__1__ CO
__1__
3
__1__ Ca __1__
__2__ Cl __1__
Both the sodium count and the chloride count can be fixed by placing a 2 coefficient
before sodium chloride.
Na
CO
(aq) + CaCl
(aq)
→
CaCO
(s) + 2NaCl(aq)
2
3
2
3
__2__ Na __2__
__1__ CO
__1__
3
__1__ Ca __1__
__2__ Cl __2__
Additionally, the products for ionic compounds, such as the reaction above, can be
predicted by switching the cation on the reactant side with the other anion of the other
cation. The anions switch places.
Try predicting the products for this reaction:
Na
CO
(aq) + CaCl
(aq)
→
2
3
2
Answer: Na
CO
(aq) + CaCl
(aq)
→ NaCl(aq) + CaCO
(s)
2
3
2
3
In this case, the products are correctly written because the charge of the cation matches
the charge of the anion. The reaction is not balanced, so follow the steps in the previous
example to balance the reaction after the products are correctly written.
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