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# Balancing Equations help watch

1. In the preview, this is an equation I have.

I know that a = 2 as there are 2 Cr atoms.

The answer states that 'to balance the charge, b = 8

How is that possible?

This is apparently GCSE/A level but I can't see how.

Thanks.
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2. (Original post by nwmyname)
In the preview, this is an equation I have.

I know that a = 2 as there are 2 Cr atoms.

The answer states that 'to balance the charge, b = 8

How is that possible?

This is apparently GCSE/A level but I can't see how.

Thanks.
You balance this using the redox half equations for the oxidation and reduction.

1. Construct the reduction half-equation, adding in hydrogen ions and water molecules as required.
2. Construct the oxidation half-equation, adding in hydrogen ions and water molecules as required.
3. Multiply the two equations by suitable coefficients to equalise the electrons
4. Add the results together and cancel out common terms.
3. 2 ways around it,both similar.

Both make use of changes of oxidation numbers being balanced.

Can use half equations as that would be the easiest to see and cancel out from scratch. Most data book also has these half equations ready.

Or u can balance from scratch like u did for a and b so far.

Depends on how "good" you are.

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