Respuesta :
MgSO4.7H2O
First of all, we need to calculate the molar mass of this molecule, using the periodic table.
Let's take each atomic mass of the elements that form this molecule from the periodic table.
Mg = 24.30 u
S = 32.06
O = 15.99 u
H = 1.007 u
Now, we have to do this:
Molar mass (g/mol) = 1 x 24.30 + 1 x 32.06 + 4 x 15.99 + 14 x 1.007 + 7 x 15.99
Molar mass = 246.3 g/mol
We have to be careful with this result because 246.3 g is the mass of 1 mole of MgSO4.7H2O and we want the mass of 1 formula unit or molecule.
Pay attention to this:
1 mole of MgSO4.7H2O = 246.3 g = 6.022 x 10^23 formula units or molecules of MgSO4.7H2O
(We want the mass of 1 molecule and we have just calculated the mass of 6.022x10^23 molecules)
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For 1 formula unit or molecule:
246.3 g of MgSO4.7H2O ------------- 6.022 x 10^23 formula units or molec.
x ------------- 1 formula unit or molec.
[tex]x\text{ = }\frac{1formula\text{ unit x 246.3 g}}{6.022x10^{23}formula\text{ units}}=4.09x10^{-22}g[/tex]Answer: The mass of 1 formula unit or molecule of MgSO4.7H2O = 4.09x10^-22 g
