Question

A compound of Xand Y has the empirical formula xy2.its vapour density is equal to its empirical formula weight.determine its molecular formula

Answer 1

In the above question it is given that empirical weight=vapour density
let emprical weight be z
we know that 2× Vapour density=Molecular mass
Molecular mass=2z
Now Molecular formula=Molecular mass÷Empirical mass×Empirical formula
molecular formula=2z÷z×xy2=2xy2

Answer 2

The molecular formula of the compound is $x_{2}y_{4}$ .

• molecular mass of a compound = 2 * (vapour density of the compound)

• Given, empirical formula = $x_{}y_{2}$
• Let empirical weight be m.
• Then, the Molecular mass of the compound

                          = 2 * (vapour density of the compound)

                          = 2 * m

                          = 2m

• Molecular formula of the compound =

             (molecular mass) / (empirical mass) * (empirical formula)

         = (2m / m) * $x_{}y_{2}$

         = 2 * $x_{}y_{2}$

         =  $x_{2}y_{4}$