How to balance the following redox problems using both methods?
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K2Cr2O7 + HI => CrI3 + KI + I2 + HOH
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K2Cr2O7 + H2C2O4 + HCl => CrCl3 + CO2 + KCl + HOH
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Sb2(SO4)3 + KMnO4 + HOH => H3SbO4 + K2SO4 + MnSO4 + H2SO4
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Mn(NO3)2 + NaBiO3 + HNO3 => Bi(NO3)2 + HMnO4 + NaNO3 + HOH
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K2Cr2O7 + HI => CrI3 + KI + I2 + HOH
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K2Cr2O7 + H2C2O4 + HCl => CrCl3 + CO2 + KCl + HOH
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Sb2(SO4)3 + KMnO4 + HOH => H3SbO4 + K2SO4 + MnSO4 + H2SO4
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Mn(NO3)2 + NaBiO3 + HNO3 => Bi(NO3)2 + HMnO4 + NaNO3 + HOH
2 Answers
WARNING! Long answer! Here's how to balance Part 3. by the oxidation number method.
Explanation:
We start with the unbalanced equation:
Step 1. Identify the atoms that change oxidation number
The changes in oxidation number are:
Step 2. Equalize the changes in oxidation number
We need 5 atoms of
Step 3. Insert coefficients to get these numbers
Step 4. Balance
We have fixed 4
Step 5. Balance
We have fixed 15
Step 6. Balance
We have fixed 76
Every formula now has a coefficient. The equation should be balanced.
Step 7. Check that all atoms are balanced.
The balanced equation is
WARNING! Long answer! Here's how to balance Part 3. by the ion-electron method.
Explanation:
We must first convert the "molecular" equation to a skeletont ionic equation.
The molecular equation is
To get the ionic equation, we write every ionic substance as separate ions.
We ignore the coefficients, because they will come back in during the balancing process.
To get the skeleton ionic equation, we eliminate every ion that occurs on both sides of the equation.
We also eliminate
The skeleton ionic equation is
We see that
Now we are ready to balance the equation.
Step 1: Write the two half-reactions.
Step 2: Balance all atoms other than
Done.
Step 3: Balance
Step 4: Balance
Step 5: Balance charge.
Step 6: Equalize electrons transferred.
Step 7: Add the two half-reactions.
Step 8: Check mass balance.
Step 9: Check charge balance.
The ionic equation is balanced.
Now we reinsert the spectator ions to get the molecular equation.
We would have to add 2.5
We multiply the ionic equation ×2 and then add the spectator ions.
Let's rewrite this as
The balanced molecular equation is