A carbon compound contains 12.8% Carbon, 2.1% Hydrogen, 85.1% Bromine. The molecular weight of the compound is 187.9. Calculate the molecular formula.

Explanation

Step 1: Percentage composition of the elements present in the compound.
`{:(C,H,Br),(12.8,2.1,85.1):}`
Step 2: Dividing with the respective atomic weights of the elements.
`{:((12.8)/(12),(2.1)/(1),(85.1)/(80)),(1.067,2.1,1.067):}`
Step 3: Dividing by the smallest number to get simple atomic ratio.
`{:((1.067)/(1.067),(2.1)/(1.067),(1.067)/(1.067)),(1,2,1):}`
The empirical formula is `CH_(2)Br`
Empricial formula weight `12 + (2 xx 1) + 80 = 94`
The molecular weight = 187.9 (given)
`therefore n=(187.9)/(94)=2`
`"The molecular formula" = "(empirical formula)"_(2)`
`(CH_(2)Br)_(2)=C_(2)H_(4)Br_(2)`