# Amount in mol of compound ions

1. Dec 19, 2007

### aham925925

[SOLVED] Amount in mol of compound ions

This is just a quick question as it has slipped my mind..

Does anyone know how you would find the mol of a compound ion (ie - SO42- (sulfate ion)), if you are given the mol of the whole compound (in my case it is K2SO4)

I know to find single ions and atoms (ie of potassium and Oxygen) you just multiply their number by the amount of mol, however i am less sure of the compound ions...

Do you treat the compound ion, in this case...as having a subscript of 1? therefore you would multiply the amount in mol by 1?

thank you..

2. Dec 20, 2007

### chemisttree

I think you have solved your own problem.

3. Dec 20, 2007

### aham925925

Yeah i may have...haha

The problem is...I'm making sure because the answer at the back of my book I know is wrong...So i have nothing to check against

4. Dec 20, 2007

### rocomath

what is the actual question?

5. Dec 20, 2007

### chickendude

Some dimensional analysis makes it intuitive

$$#mol (K_2SO_4) * \frac{1 mol SO_4}{1 mol K_2SO_4}$$

That fraction is equal to 1 since there is exactly 1 mol of SO4 in every mol of K2SO4

The mol K2SO4 cancel out and you have what you're looking for

6. Dec 20, 2007

### aham925925

The given question was not worded well

But i understand now that in a compound such as K2SO4, you would treat SO4^2- as one ion in this compound....therefore you would multiply 1 by the number of mol there is of K2SO4..

Problem solved.....thanks guys