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twoudly · Oct 6, 2010, 07:24 AM

Unknown008 · Oct 6, 2010, 07:51 AM

The relative formula mass of CuSO4.5H2O is:

Mr = 63.5 + 32 + 64 + 5(18) = 249.5

So, 249.5 g of CuSO4.5H2O contains 1 mol of substance.

Find the number of moles of substance $9.5\times 10^{-3}g$ contain.
Number of moles = $\frac{9.5\times 10^{-3}}{249.5} = 3.81 \times 10^{-5}$ mol.

Now, each mole of substance holds 9 moles of oxygen atoms.
Find the number of moles of oxygen atoms in your amount of moles above.

1 mol --> 9 moles of O
$3.81\times 10^{-5} \to 9\times 3.81\times 10^{-5} mol = 3.427 \times 10^{-4}$ mol

Now, 1 mol means $6.02\times 10^{23}$

Find how many does $3.427 \times 10^{-4}$ mol mean.

Post what you get! :)