Writing And Balancing Chemical Reactions, Stoichiometry, Limiting Reactants Worksheet With Answers - Chem110 Page 5
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8CHEM110 Week 5 Notes (Stoichiometry)
Page 5 of 8
Balance this reaction:
H
SO
(aq) + NaOH(aq)
→
2
4
Answer: This is an acid-base reaction, and predicting the products follows the same
format as for reaction with ionic compounds.
H
SO
(aq) + NaOH(aq)
→
NaSO
+ HO
2
4
4
The compounds as products are not properly written because they are not charge
balanced. For the first product, sulfate is -2, so two +1 sodium ions are needed. The
correct formula for sodium sulfate is Na
SO
. For the second product, H is +1 and O is
2
4
-2, so the correct formula is H
O (or water). The reaction with correctly written products
2
appears below.
H
SO
(aq) + NaOH(aq)
→
Na
SO
(aq) + H
O(l)
2
4
2
4
2
Now, the reaction can be balanced.
H
SO
(aq) + NaOH(aq)
→
Na
SO
(aq) + H
O(l)
2
4
2
4
2
__1__ Na __2__
__1__ SO
__1__
4
__3__ H __2__
__1__ O __1__
Fix the sodium count by adding a 2 coefficient to sodium hydroxide.
H
SO
(aq) + 2NaOH(aq)
→
Na
SO
(aq) + H
O(l)
2
4
2
4
2
__2__ Na __2__
__1__ SO
__1__
4
__4__ H __2__
__2__ O __1__
The remaining challenge is to balance H and O. Both of these appear as bound atoms in
H
O. Adding a 2 coefficient to water balances the reaction.
2
H
SO
(aq) + 2NaOH(aq)
→
Na
SO
(aq) + 2H
O(l)
2
4
2
4
2
__2__ Na __2__
__1__ SO
__1__
4
__4__ H __4__
__2__ O __2__
Stoichiometry
The principle of stoichiometry depends on the law of conservation of matter. It depends
on the chemical reaction being properly balanced. Stoichiometry allows us to predict the
amounts and masses of reactants needed and products produced by a chemical reaction.
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