Question

Compound composed of sulfur and fluorine is found to contain 45.77% by mass of sulfur is the molar mass of the compound is 140.12 g per mole what is its molecular formula

Answer 1

Answer: Molecular formula is S2F4

Explanation: Assume mass of sample is 100 g.

Then mass of S is 45.77 g and amount of substance is

n = m/M = 45.77 g / 32.07 g/mol = 1.427 mol

MAss of F is 54.23 g and n = 54.23 g / 19 g/mol = 2.854

n(S( : n(F) = 1.427 : 2.854 | : 1.427 gives proportion

n(S) : n(F) = 1:2 , empirical formula is also (SF2)x

Now M(SF2) = 32.07 + 2·19 = 70.07 g/mol

x = 140.12 / 70.07 = 2