A 2.500 gram sample of CuSO4 • xH2O is heated until there is no change in the mass of the residue. The residue
weighs 1.598 grams. What is the value of x
The change in mass is equal to the mass of the residue subtracted from the initial mass of the sample:
change in mass = 2.500 g - 1.598 g = 0.902 g
Since the residue is only the anhydrous salt, the difference in mass is due to the loss of water molecules.
The molar mass of CuSO4 is 159.609 g/mol, and the molar mass of H2O is 18.015 g/mol.
To calculate the value of x, we need to find the number of moles of water lost and then divide by the number of moles of CuSO4:
moles of CuSO4 = mass of CuSO4 / molar mass of CuSO4 = 1.598 g / 159.609 g/mol = 0.010 g/mol
moles of H2O lost = change in mass / molar mass of H2O = 0.902 g / 18.015 g/mol = 0.050 mol
Now, we can divide the moles of water lost by the moles of CuSO4 to find the value of x:
x = moles of H2O lost / moles of CuSO4 = 0.050 mol / 0.010 mol = 5
Therefore, the value of x is 5.