Question

Phosgene has the elemental compositions of 12.14% carbon, 16.17 % oxygen, and 71.69% chlorine by mass.

(a) Determine the empirical formula of this compound, from the data provided.
(b) The molar mass of phosgene is 98.9 g/mol. Determine the molecular formula, using your answer in (a). Hint: It is either the empirical formula or some multiple of the subscripts. Show or explain your logic in this determination.

Answer 1

a) COCl₂.

b) The molecular formula is COCl₂.

Step-by-step explanation:

To obtain empirical formula of phosgene you should divide elemental compositions over atomic mass of each atom, and divide these results between the smallest, thus:

C = 12,14%/12,01 = 1,01

O = 16,17%/16 = 1,01

Cl = 71,69%/35,45 = 2,02

Empirical formula:

C = 1,01/1,01 = 1

O = 1,01/1,01 = 1

Cl = 2,02/1,01 = 2

C₁O₁Cl₂ ≡ COCl₂

b) You need to find the molar mass of the empirical formula to determine the ratio of the real formula, thus:

1×C 12,01g/mol =

1×O 16 g/mol =

2×Cl 35,35g/mol = 98,91g/mol

As real molecular mass is 98,9 g/mol. The molecular formula: COCl₂

I hope it helps!