What is the empirical formula and name of this hydrate?
A 7.75g sample of a hydrate of MgCl2 was heated until no more water was given off. The mass of the anhydrous salt is 3.63g. What is the empirical formula and name of this hydrate?
- Bobby_ThinLv 78 months ago
The mass of the anhydrous MgCl2 salt is 3.63g = 3.630g / 95.2110 g/mol = 0.03812 moles
mass of water driven off = 7.75 g - 3.63 g = 4.12 g or 4.12g / 18 g / mol H2O = 0.2289
molar ratio MgCl2 : H2O = 0.03812 : 0.2289 = 1:6 ( dividing by the smaller number)
empirical formula is MgCl2*6H2O
- davidLv 78 months ago
1, find molar mass (MM1) of MgCl2 ... find molar mass (MM2) H2O
2. 7.75 - 3.63 = 4.12g H2O
3. 3.63 / MM1 = moles MgCl2
4. 4.12 / MM2 = moles H2O
5. moles H2O / moles MgCl2 = multiplier (x)of H2O <<< round as appropriate
6. MgCl2 . xH2O <<< emp. formula
7. write the name using the approp. prefix ... 1H2O = monohydrae
2H2O = dihydrate ... etc ..