Kiera asked in Science & MathematicsChemistry · 8 months ago

# 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?

Relevance
• 8 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

moles

molar ratio MgCl2 : H2O = 0.03812 : 0.2289 = 1:6 ( dividing by the smaller number)

empirical formula is MgCl2*6H2O

• david
Lv 7
8 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 ..