Question

An unknown compound with a molar mass of 155.06 g/mol consists of 46.47% C, 7.80% H, and 45.72% CI. Find the molecular formula for the compound.

Answer 1

we have mass of each elements as:

C: 46.47 g

H: 7.8 g

Cl: 45.72 g

Divide by molar mass to get number of moles of each:

C: 46.47/12.01 = 3.8693

H: 7.8/1.008 = 7.7381

Cl: 45.72/35.45 = 1.2897

Divide by smallest to get simplest whole number ratio:

C: 3.8693/1.2897 = 3

H: 7.7381/1.2897 = 6

Cl: 1.2897/1.2897 = 1

  

So empirical formula is:C3H6Cl

Molar mass of C3H6Cl,

MM = 3*MM(C) + 6*MM(H) + 1*MM(Cl)

= 3*12.01 + 6*1.008 + 1*35.45

= 77.528 g/mol

Now we have:

Molar mass = 155.06 g/mol

Empirical formula mass = 77.528 g/mol

Multiplying factor = molar mass / empirical formula mass

= 155.06/77.528

= 2

So molecular formula is:C6H12Cl2

Answer: C6H12Cl2