Question

A sample of fluorine has a mass of 27.2 grams.

How many f atoms are there in the sample?

atoms

How many f2 molecules are there in the sample?

molecules

Answer 1

Ans. Fluorine naturally exists in diatomic gas as F₂. So, the sample of fluorine is actually F₂ gas.

Moles of F₂ in sample = Mass / Molar mass

                                    = 27.2 g / (37.9968064 g/ mol)

                                    = 0.71585 mol

#I. 1 mol F₂ gas consists of 2 mol F-atoms.

So,

            Moles of F-atoms = 2 x moles of F₂

                                    = 2 x 0.71585 mol

                                    = 1.4317 mol

Now,

            Number of F-atoms = Moles of F-atom x Avogadro number

                                    = 1.4317 mol x (6.022 x 10²³ atoms/ mol)

                                    = 8.622 x 10²³ atoms

#II. We have, moles of F₂ = 0.71585 mol

Now,

            Number of F₂ molecules = Moles of F₂ x Avogadro number

                                    = 0.71585 mol x (6.022 x 10²³ molecules/ mol)

                                    = 4.311 x 10²³ molecules