Here it is
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We know that mass of carbon atom in amu is 12 amu and in grams is 12 grams.
So now 12 amu = 1atom
12 grams = 1 mole of carbon = 6.022*10^23 atoms of carbon (NA Avogadro's number)
1 atom of carbon mass = 12 amu = 12 g /NA
Solve it
1amu = 1g/NA
You can use any element in place of carbon. Remember mass of 1 atom is in amu and 1 mole is in grams .But value of mass will be same as mentioned in the periodic table.
Like 1 atom of oxygen is 16 amu but 1 mole of oxygen atoms is 16 g
I give a thought process and try to solve it after that,
Formula of the hydrate is CuSO4.5H2O means 1 mole of CuSO4 has 5 moles of water.
Now grams of hydrated CuSO4 is given to us
Convert Grams of the Copper sulphate pentahydrate to moles of Copper sulphate pentahydrate to moles of water and then to molecules of water.
Grams to moles use molar mass for conversion
moles to molecules use Avogadro's number.