Question

The empirical formula of a compound is COCl2 and its molecular mass is 90.00u. Find out the molecular formula of that compound.

Answer 1

Answer:

Explanation:

MOLECULAR FORMULA = (molecular mass/emperical formula mass)    

                                                                     ×                                                                            

                                                         empercal formula

                                          =(99/99)×COCL2

                                            = 1 ×COCL2

                                            ≅COCL2

Answer 2

Mistake in the question :

• The molecular mass must be 99.00 u .

Correct question :

• The empirical formula of a compound is COCl2 and its molecular mass is 99.00 u. Find out the molecular formula of that compound.

Given :

• Emperical formula = $\tt COCl_2$
• Molecular mass = 99 u

To find :

• Molecular formula

Solution :

Let us first find the molecular formula mass :

Mass of $\tt COCl_2$ = Mass of C + Mass of O + 2 × Mass of Cl

= 12 + 16 + 2 × 35.5

= 28 + 71

= 99 u .

n = Molecular mass/ emperical mass

= 99 / 99

n = 1

Now , molecular formula = n × Emperical formula

= 1 × $\tt COCl_2$

= $\tt COCl_2$

Therefore , the molecular formula is same as Emperical formula .

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• Emperical formula : It gives the simplest whole number ratio in which atoms of different elements are present in a compound . For example : in glucose , the emperical formula is $\tt CH_2O$ .

• Molecular formula : It gives the exact number of atoms of different elements present in a molecule of a compound . For example : the molecular formula of glucose is $\tt C_6H_{12}O_6$ .