Using oxidation states to balance equations

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16dan2life
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Report Thread starter 9 years ago
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Hey, I'm stuck with using oxidation states to balance equations
Can anyone help?

Can someone please tell me step by step how to balance either or both of these equations using oxidation states?

1) Cl2 + NaOH ——> NaClO3 + NaCl + H2O

2) Sn + HNO3 ——> SnO2 + NO2 + H2O
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clownfish
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1) chlorine is going from 0 in Cl2, to +5 in NaClO3 and -1 in NaCl and all other species are remaining in the same oxidation state.

imagine if an atom if chlorine is going to lose 5e to form a +5 state, then we need 5 of the atoms of chlorine that want to gain 1e to form the Cl- state to balance this, so multiply the NaCl by 5.

Cl2 + NaOH ——> NaClO3 + 5NaCl + H2O

Now make the no of chlorines on both sides the same

3Cl2 + NaOH ——> NaClO3 + 5NaCl + H2O

Balance the sodiums:

3Cl2 + 6NaOH ——> NaClO3 + 5NaCl + H2O

Balance the hydrogens:

3Cl2 + 6NaOH ——> NaClO3 + 5NaCl + 3H2O

Check oxygens are are balanced. Then you're done.

----
2) the tin is going from an oxidation state of zero to an oxidation state of +4 (we can assume that oxygen is -2 in this case).
The nitrogen is going from an oxidation state of +5 to +4. All other species remain in the same oxidation state.

so tin is losing 4 electrons and nitrogen is gaining one electron

so it will take 4 nitrogens to accept all the electrons that tin has to give. Therefore make sure there are 4 N on each side.

Sn + 4HNO3 ---> SnO2 + 4NO2 + H2O

Now the hydrogens are not balanced so multiply the water by 2


Sn + 4HNO3 ---> SnO2 + 4NO2 + 2H2O

Quick check and all species are balanced.

----

This took me a long time to write - I hope it makes sense and has helped a bit!
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16dan2life
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(Original post by clownfish)
1) chlorine is going from 0 in Cl2, to +5 in NaClO3 and -1 in NaCl and all other species are remaining in the same oxidation state.

imagine if an atom if chlorine is going to lose 5e to form a +5 state, then we need 5 of the atoms of chlorine that want to gain 1e to form the Cl- state to balance this, so multiply the NaCl by 5.

Cl2 + NaOH ——> NaClO3 + 5NaCl + H2O

Now make the no of chlorines on both sides the same

3Cl2 + NaOH ——> NaClO3 + 5NaCl + H2O

Balance the sodiums:

3Cl2 + 6NaOH ——> NaClO3 + 5NaCl + H2O

Balance the hydrogens:

3Cl2 + 6NaOH ——> NaClO3 + 5NaCl + 3H2O

Check oxygens are are balanced. Then you're done.

----
2) the tin is going from an oxidation state of zero to an oxidation state of +4 (we can assume that oxygen is -2 in this case).
The nitrogen is going from an oxidation state of +5 to +4. All other species remain in the same oxidation state.

so tin is losing 4 electrons and nitrogen is gaining one electron

so it will take 4 nitrogens to accept all the electrons that tin has to give. Therefore make sure there are 4 N on each side.

Sn + 4HNO3 ---> SnO2 + 4NO2 + H2O

Now the hydrogens are not balanced so multiply the water by 2


Sn + 4HNO3 ---> SnO2 + 4NO2 + 2H2O

Quick check and all species are balanced.

----

This took me a long time to write - I hope it makes sense and has helped a
bit!


Thanks!! helped me a lot
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sroas
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please help me to bakance this n.o Cl2 NH3 --> Cl- N2 H2O
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issie rose
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currently teaching myself this in quarantine and it helped so much! thank you
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