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?

2 Answers

Relevance
  • 4 weeks 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
    4 weeks 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 ..

Still have questions? Get your answers by asking now.