when 1.40 g of hydrated magnesium salfate is heated to constant mass, 0.68 g of the anhydrous salt remains. find the formula for the hydrated magnesium sulfate.
MgSO4*xH2O ==> MgSO4 + xH2O
grams water = 1.40 - 0.68 = ??
mols H2O = ??/molar mass H2O.
mols MgSO4 = 0.68/molar mass MgSO4.
Then find ratio of mol H2O per 1 mol MgSO4. That will be x. Post your work if you get stuck.
To find the formula for the hydrated magnesium sulfate, we can follow these steps:
1. Determine the mass of water lost during heating:
grams of water = mass of hydrated salt - mass of anhydrous salt
= 1.40 g - 0.68 g
= 0.72 g
2. Convert the mass of water lost to moles:
mols H2O = grams of water / molar mass of water
The molar mass of water (H2O) is 18.015 g/mol.
Therefore, mols H2O = 0.72 g / 18.015 g/mol
≈ 0.04 mol
3. Convert the mass of anhydrous salt to moles:
mols MgSO4 = mass of anhydrous salt / molar mass of MgSO4
The molar mass of magnesium sulfate (MgSO4) is 120.366 g/mol.
Therefore, mols MgSO4 = 0.68 g / 120.366 g/mol
≈ 0.005 mol
4. Determine the ratio of moles of water to moles of anhydrous salt (x):
This ratio will give us the value of 'x' in the formula MgSO4 * xH2O.
x = mols H2O / mols MgSO4
= 0.04 mol / 0.005 mol
= 8
Therefore, the formula for the hydrated magnesium sulfate is MgSO4 * 8H2O.