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Help with percent composition

Ok- I understand how to do percent composition except:

If you have CuSO4 . 5H2O, do you distribute the 5 to the H2 and get 10 H atoms and then distribute it to the O and get 5 O atoms?

Nicole S.
student - Falls Church, Virginia
2005

Technically, the dot 5H2O means that you have 5 molecules of water mechanically attached (water of hydration) to the copper sulphate. For most calculations, you would consider it as water rather than atoms of H and O. You do consider it in the weight when you are trying to weigh out an amount of the hydrated material to get a given amount of the copper or the copper sulphate ⇦this on eBay or Amazon [affil links] or the sulphate.

James Watts
- Navarre, Florida
2005