Question

A sample of a gaseous binary compound of sulfur and fluorine weighing 0.989 g is decomposed to give 0.293 g of solid S. In a separate experiment, the molar mass of the compound is determined to be 108 g/mol. Determine the molecular formula of the compound. Enter S before F.

Answer 1

we have mass of each elements as:

S: 0.293 g

F: 0.989 g - 0.23 g = 0.696 g

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

S: 0.293/32.07 = 0.0091

F: 0.696/19.0 = 0.0366

Divide by smallest to get simplest whole number ratio:

S: 0.0091/0.0091 = 1

F: 0.0366/0.0091 = 4

So empirical formula is:SF4

Molar mass of SF4,

MM = 1*MM(S) + 4*MM(F)

= 1*32.07 + 4*19.0

= 108.07 g/mol

Now we have:

Molar mass = 108.0 g/mol

Empirical formula mass = 108.07 g/mol

Multiplying factor = molar mass / empirical formula mass

= 108.0/108.07

= 1

So molecular formula is:SF4

Answer: SF4