The chemical analysis of a compound having a molecular mass 188 gives, C=12.8%, H=2.1%, and Br=85.1%. Its molecular formula is:
Correct answer: B. C2H4Br2
- A. CH2Br
- B. C2H4Br2
- C. C2H4Br
- D. CH2(Br)2
- E. C2H2(Br)3
Explanation
To determine the molecular formula, first calculate the empirical formula based on the given percentage composition:Convert the percentage of each element to mass: 12.8 g of C, 2.1 g of H, and 85.1 g of Br.Convert mass to moles: C (12.8 g / 12.01 g/mol), H (2.1 g / 1.008 g/mol), Br (85.1 g / 79.904 g/mol).Find the mole ratio by dividing each by the smallest number of moles.The empirical formula is CH2Br.The empirical formula mass is approximately 94.5 g/mol.Divide the molecular mass (188 g/mol) by the empirical formula mass (94.5 g/mol) to find the multiplier, which is 2.Multiply the empirical formula by this factor to get the molecular formula: C2H4Br2.Options A, C, D, and E do not match the molecular mass or fail to maintain the correct elemental ratio.
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