Calculate the percentage by mass of water of crystallization in MgSO4.7H2O
To calculate the percentage by mass of water of crystallization in MgSO4.7H2O, we need to find the molar mass of MgSO4.7H2O and the molar mass of the 7 moles of H2O in the compound, and then compare the mass of the water to the mass of the entire compound.
First, let's find the molar mass of MgSO4:
Mg = 24.3 g/mol
S = 32.1 g/mol
O = 16.0 g/mol (We have 4 oxygen atoms in SO4, so we will multiply by 4)
Molar mass of MgSO4 = 24.3 g/mol (Mg) + 32.1 g/mol (S) + (4 x 16.0 g/mol (O))
Molar mass of MgSO4 = 24.3 + 32.1 + 64.0
Molar mass of MgSO4 = 120.4 g/mol
Next, let's find the molar mass of 7 moles of H2O in the compound:
H = 1.0 g/mol (We have 2 hydrogen atoms in H2O, so we will multiply by 2)
O = 16.0 g/mol
Molar mass of H2O = (2 x 1.0 g/mol (H)) + 16.0 g/mol (O)
Molar mass of H2O = 2.0 + 16.0
Molar mass of H2O = 18.0 g/mol
Now, we have 7 moles of H2O in the compound, so the mass of water is:
Mass of 7 moles of water = 7 x 18.0 g/mol
Mass of 7 moles of water = 126.0 g/mol
To find the molar mass of MgSO4.7H2O, we will add the molar mass of MgSO4 and the mass of 7 moles of water:
Molar mass of MgSO4.7H2O = 120.4 g/mol (MgSO4) + 126.0 g/mol (7H2O)
Molar mass of MgSO4.7H2O = 246.4 g/mol
Now, we will calculate the percentage by mass of water in MgSO4.7H2O:
Percentage by mass of water = (Mass of 7 moles of water) / (Molar mass of MgSO4.7H2O) x 100
Percentage by mass of water = (126.0 g/mol) / (246.4 g/mol) x 100
Percentage by mass of water ≈ 51.14 %
So, the percentage by mass of water of crystallization in MgSO4.7H2O is approximately 51.14%.