CHE 141: Principles of Chemistry

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Balancing chemical equations

You may have to complete some of these equations by supplying any necessary products or reactants. The "??" will indicate to you such occasions.
If a reaction is described in words, provide the formulas for the reactants or products and balance the equation.

Click on the equation number to go to the answer.

1   H2 + O2   H2O
2   S8 + O2   SO3
3   HgO   Hg + O2
4   Zn + HCl   ZnCl2 + H2
5   C10H16+ Cl2   C + HCl
6   Na + H2O   NaOH + H2
7   Si2H3 + O2   SiO2 + H2O
8   Fe + O2   Fe2O3
9   C7H6O2 + O2   ?? + ??
10   FeS2 + O2   Fe2O3 + ??
11   Fe2O3 + H2   Fe + H2O
12   K + Br2   ??
13   C2H2 + O2   CO2 + H2O
14   C3H8 + O2   ?? + H2O
15   C7H16 + O2   CO2 + H2O
16   H2O2   H2O + O2
17   SiO2 + HF   SiF4 + H2O
18   KClO3   KCl + O2
19   KClO3   KClO4 + KCl
20   P4O10 + H2O   H3PO4
21   Sb + O2   Sb4O6
22   Fe2O3 + CO   Fe + CO2
23   PCl5 + H2O   HCl + H3PO4
24   H2S + Cl2   S8 + HCl
25   Fe + H2O   Fe3O4 + H2
26   N2 + H2   NH3
27   N2 + O2   N2O
28   CO2 + H2O   C6H12O6 + O2
29   SiCl4 + H2O   H4SiO4 + HCl
30   H3PO4   H4P2O7 + H2O
31   CO2 + NH3   (NH2)2CO + H2O
32   Al(OH)3 + H2SO4   Al2(SO4)3 + H2O
33  

Solutions of Iron (III) sulfate and potassium hydroxide were mixed:

   ?? + ??
34   H2SO4 + HI   H2S + I2 + H2O 
35  

Aluminum was reacted with Iron (II) oxide

   ?? + ??
36  

Solutions of sodium carbonate and hydrochloric acid were mixed:

   ?? + ?? + ??
37   P4 + O2   P2O5
38   K2O + H2O   KOH
39   Al + O2   Aluminum oxide
40   Sodium oxide + H2O   Sodium hydroxide
41   C + H2O   CO + H2
42   H3AsO4   As2O5 + H2O
43  

Solutions of aluminum sulfate and calcium hydroxide were mixed:

   ?? + ??
44  

Solutions of Iron (III) chloride and ammonium hydroxide were mixed:

   ?? + ??
45   Ca3(PO4)2 + SiO2   Calcium silicate + Phosphorus pentoxide
46   N2O5 + H2O   ??
47   Al + HCl   ?? + H2
48   H3BO3   H4B6O11 + H2O
49   Mg + N2   Mg3N2
50   NaOH + Cl2   NaCl + NaClO + H2O
           

Answers

Even though it is accepted convention to not write the number 1 if only one mole of a reactant or product is present, please make it a habit to write the number 1 (see below for examples). 
Doing this tells me that you know it is 1 and you are not leaving it blank because you don't know!!

Click on the equation number to go back to the top.
1   2H2 + 1O2   2H2O
2   1S8 + 12O2   8SO3
3   2HgO   2Hg + 1O2
4   1Zn + 2HCl   1ZnCl2 + 1H2
5   1C10H16+ 8Cl2   10C + 16HCl
6   2Na + 2H2O   2NaOH + 1H2
7   4Si2H3 + 11O2   8SiO2 + 6H2O
8   4Fe + 3O2   2Fe2O3
9   2C7H6O2 + 15O2   14CO2 + 6H2O
10   4FeS2 + 11O2   2Fe2O3 + 8SO2
11   1Fe2O3 + 3H2   2Fe + 3H2O
12   2K + 1Br2   2KBr
13   2C2H2 + 5O2   4CO2 + 2H2O
14   1C3H8 + 5O2   3CO2 + 4H2O
15   1C7H16 + 11O2   7CO2 + 8H2O
16   2H2O2   2H2O + 1O2
17   1SiO2 + 4HF   1SiF4 + 2H2O
18   2KClO3   2KCl + 3O2
19   4KClO3   3KClO4 + 1KCl
20   1P4O10 + 6H2O   4H3PO4
21   4Sb + 3O2   1Sb4O6
22   1Fe2O3 + 3CO   2Fe + 3CO2
23   1PCl5 + 4H2O   5HCl + 1H3PO4
24   8H2S + 8Cl2   1S8 + 16HCl
25   3Fe + 4H2O   1Fe3O4 + 4H2
26   1N2 + 3H2   2NH3
27   2N2 + 1O2   2N2O
28   6CO2 + 6H2O   1C6H12O6 + 6O2
29   1SiCl4 + 4H2O   1H4SiO4 + 4HCl
30   2H3PO4   1H4P2O7 + 1H2O
31   1CO2 + 2NH3   1(NH2)2CO + 1H2O
32   2Al(OH)3 + 3H2SO4   1Al2(SO4)3 + 6H2O
33  

Solutions of Iron (III) sulfate and potassium hydroxide were mixed:
1Fe2(SO4)3 + 6KOH

   2Fe(OH)3 + 3K2SO4
34   1H2SO4 + 8HI   1H2S + 4I2 + 4H2O 
35  

Aluminum was reacted with Iron (II) oxide:
2Al + 3FeO

   3Fe + 1Al2O3
36  

Solutions of sodium carbonate and hydrochloric acid were mixed:
1Na2CO3 + 2HCl

   2NaCl + CO2 + H2O
37   1P4 + 5O2   2P2O5
38   1K2O + 1H2O   2KOH
39   4Al + 3O2   Aluminum oxide: 2Al2O3
40   Sodium oxide: 1Na2O + 1H2O   Sodium hydroxide: 2NaOH
41   1C + 1H2O   1CO + 1H2
42   2H3AsO4   1As2O5 + 3H2O
43  

Solutions of aluminum sulfate and calcium hydroxide were mixed:
1Al2(SO4)3 + 3Ca(OH)2

   2Al(OH)3 + 3CaSO4
44  

Solutions of Iron (III) chloride and ammonium hydroxide were mixed:
1FeCl3 + 3NH4OH

   1Fe(OH)3 + 3NH4Cl
45   1Ca3(PO4)2 + 3SiO2  

Calcium silicate + Phosphorus pentoxide:
3CaSiO3 + 1P2O5
46   1N2O5 + 1H2O   2HNO3
47   2Al + 6HCl   2AlCl3 + 3H2
48   6H3BO3   1H4B6O11 + 7H2O
49   3Mg + 1N2   1Mg3N2
50   2NaOH + 1Cl2   1NaCl + 1NaClO + 1H2O
           

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