Try to balance each of the following reactions.  Click on the arrow to see the answer

NaOH + CO₂ ® Na₂CO₃ + H₂O
Cu₂S + O₂ ® Cu + SO₂
Zn + Au(CN)₂ ® Zn(CN)₂ + Au
P₄O₁₀ + H₂O ® H₃PO₄
NaN₃ ® Na + N₂
HCl + NaOH ® NaCl + H₂O
KClO₃ ® KCl + O₂
Pb(NO₃)₂ + KOH ® KNO₃ + Pb(OH)₂
S + O₂ ® SO₃
Cu(OH)₂ + CH₃CO₂H ® Cu(CH₃CO₂)₂ + H₂O
C₆H₅Cl + SiCl₄ + Na ® (C₆H₅)₄Si + NaCl
MnO₂ + HCl ® Cl₂ + MnCl₂ + H₂O
CO(NH₂)₂ + H₂O ® CO₂ + NH₃
VO + Fe₂O₃ ® FeO + V₂O₅
HNO₃ + HI ® NO + I₂ + H₂O
CuSCN + KIO₃ + HCl ® CuSO₄ + KCl + HCN + ICl + H₂O
HIO₃ + FeI₂ + HCl ® FeCl₃ + ICl + H₂O

from JChemEd v74n11p1256-7, 1270 Nov97
KMnO₄ + KI + H₂SO₄ ®  MnSO₄ + K₂SO₄ + I₂ + H₂O
KMnO₄ + Na₂SO₃ + H₂O ® MnO₂ + Na₂SO₄ + KOH
KMnO₄ + NaNO₂ + KOH ® K₂MnO₄ + NaNO₃ + H₂O
CuS + HNO₃ ® CuSO₄ + NO₂ + H₂O
Cu + HNO₃ ® Cu(NO₃)₂ + NO + H₂O
Na₂S₂O₃ + I₂® Na₂S₄O₆ + NaI
NaBr + NaBrO₃ + H₂SO₄® Na₂SO₄ + Br₂ + H₂O
K₂Cr₂O₇ + FeSO₄ + H₂SO₄® Cr₂(SO₄)₃ + Fe₂(SO₄)₃ + K₂SO₄ + H₂O
SnCl₂ + K₂Cr₂O₇ +HCl ® SnCl₄ + CrCl₃ + KCl + H₂O
KMnO₄ + HCl ® MnCl₂ + Cl₂ + KCl + H₂O
KMnO₄ + H₂O₂ + H₂SO₄® MnSO₄ + K₂SO₄ + O₂ + H₂O
KI + KClO₃ + H₂SO₄ ® I₂ + KCl + K₂SO₄ + H₂O
KNO₃ + KI + H₂SO₄ ® NO + I₂ + K₂SO₄ + H₂O
Cl₂ + KOH ® KClO₃ + KCl + H₂O
H₂O₂ + KI ® KOH + I₂
P₂I₄ + P₄ + H₂O ® PH₄I + H₃PO₄

And this one is the hardest I have found. It might help to determine the charges on Cr in each species present.
[Cr(N₂H₄CO)₆]₄[Cr(CN)₆]₃ + KMnO₄ + H₂SO₄ ® K₂Cr₂O₇ + MnSO₄ + CO₂ + KNO₃ + K₂SO₄ + H₂O

2NaOH + 1CO₂ ® 1Na₂CO₃ + 1H₂O
1Cu₂S + 1O₂ ® 2Cu + 1SO₂
1Zn + 1Au(CN)₂ ® 1Zn(CN)₂ + 1Au
1P₄O₁₀ + 6H₂O ® 4H₃PO₄
2NaN₃ ® 2Na + 3N₂
1HCl + 1NaOH ®1NaCl + 1H₂O
2KClO₃ ® 2KCl + 3O₂
1Pb(NO₃)₂ + 2KOH ®2KNO₃ + 1Pb(OH)₂
2S + 2O₂® 2SO₃
1Cu(OH)₂ + 2CH₃CO₂H ® 1Cu(CH₃CO₂)₂ + 2H₂O
4C₆H₅Cl + 1SiCl₄ + 4Na ® 1(C₆H₅)₄Si + 4NaCl
1MnO₂ + 4HCl ®1Cl₂ + 1MnCl₂ + 2H₂O
1CO(NH₂)₂ + 1H₂O ® 1CO₂ + 2NH₃
2VO + 3Fe₂O₃ ® 6FeO + 1V₂O₅
2HNO₃ + 6HI ®2NO + 3I₂ + 4H₂O
4CuSCN + 7KIO₃ + 14HCl ® 4CuSO₄ + 7KCl + 4HCN + 7ICl + 5H₂O
5HIO₃ + 4FeI₂ + 25HCl ® 4FeCl₃ + 13ICl + 15H₂O

from JChemEd v74n11p1256-7, 1270 Nov97
2KMnO₄ + 10KI + 8H₂SO₄® 2MnSO₄ + 6K₂SO₄ + 5I₂ + 8H₂O
2KMnO₄ + 3Na₂SO₃ + 1H₂O ®2MnO₂ + 3Na₂SO₄ +2KOH
2KMnO₄ + 1NaNO₂ + 2KOH ®2K₂MnO₄ + 1NaNO₃ + 1H₂O
1CuS + 8HNO₃ ® 1CuSO₄ + 8NO₂ + 4H₂O
3Cu + 8HNO₃ ® 3Cu(NO₃)₂ + 2NO + 4H₂O
2Na₂S₂O₃ + 1I₂ ® 1Na₂S₄O₆ + 2NaI
5NaBr + 1NaBrO₃ + 3H₂SO₄®3Na₂SO₄ + 3Br₂ + 3H₂O
1K₂Cr₂O₇ + 6FeSO₄ + 7H₂SO₄®1Cr₂(SO₄)₃ + 3Fe₂(SO₄)₃ + 1K₂SO₄ + 7H₂O
3SnCl₂ + 1K₂Cr₂O₇ + 14HCl ®3SnCl₄ + 2CrCl₃ + 2KCl + 7H₂O
2KMnO₄ + 16HCl ®2MnCl₂ + 5Cl₂ + 2KCl + 8H₂O
2KMnO₄ + 1H₂O₂ + 3H₂SO₄®2MnSO₄ + 1K₂SO₄ + 3O₂ + 4H₂O
The previous reaction may have more than one possible ratio sets; it appears that there are two simultaneous independent reaction listed.  Try it as simultaneous equations and you'll see what I mean!
6KI + 1KClO₃ + 3H₂SO₄®3I₂ + 1KCl + 3K₂SO₄ + 3H₂O
2KNO₃ + 6KI + 4H₂SO₄®2NO + 3I₂ + 4K₂SO₄ + 4H₂O
3Cl₂ + 6KOH ®1KClO₃ + 5KCl + 3H₂O
1H₂O₂ + 2KI ®2KOH + 1I₂
10P₂I₄ + 13P₄ + 128H₂O ®40PH₄I + 32H₃PO₄

Do you think I would just tell you the answer?  I found the "Solver" add-in for Microsoft Excel helpful...
[Cr(N₂H₄CO)₆]₄[Cr(CN)₆]₃ + KMnO₄ + H₂SO₄ ® K₂Cr₂O₇ + MnSO₄ + CO₂ + KNO₃ + K₂SO₄ + H₂O

[Syllabus 3][MHS AP Chem page]