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NTA Abhyas JEE Main2020ChemistrySome Basic Concepts of ChemistryPractice

A carbon compound contains 12.8% of carbon, 2.1% of hydrogen and 85.1% of bromine. The molecular weight of the compound is 187.9. Calculate the molecular formula of the compound. (Atomic wts: H = 1.008, C = 12.0, Br = 79.9)

Options

  1. AC H 3 B r
  2. BC H 2 B r 2 I
  3. CC 2 H 4 B r 2
  4. DC 2 H 3 B r 3

Correct answer

C. C 2 H 4 B r 2

Step-by-step solution

E l e m e n t % A t . w t R e l a t i v e n u m b e r S i m p l e r a t i o C 12.8 12 12.8 12 = 1.06 106 1.06 = 1 H 2.1 1 2.1 1 = 2.1 2.1 1.06 = 2 B r 85.1 80 85.1 80 = 1.06 1.06 1.06 = 1 E.F = C H 2 B r Wt. of E F = 12 + 2 + 80 = 94 n = M . W w t o f E F = 187.9 94 = 2 M F = E F n = C H 2 B r 2 = C 2 H 4 B r 2

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