What is the molar mass of 1-butene if 5.38 × 1016 molecules of 1-butene weigh 5.00 μg?

              Molar Mass =  56 g.mol⁻¹

Data Given:

                   Mass  =  5.00 μg  =  5.0 × 10⁻⁶ g

                   Number of Molecules  =  5.38 × 10¹⁶ Molecules

Step 1: Calculate Moles of 1-Butene:

                      As we know one mole of any substance contains 6.022 × 10²³ particles (atoms, ions, molecules or formula units). This number is also called as Avogadro's Number.

The relation between Moles, Number of Particles and Avogadro's Number is given as,

                          Moles  =  Number of Particles ÷ 6.022 × 10²³

Putting values,

                          Moles  =  5.38 × 10¹⁶ Molecules ÷ 6.022 × 10²³

                          Moles  =  8.93 × 10⁻⁸ Moles

Step 2: Calculate Molar Mass of 1-Butene:

As,

                          Mole  =  Mass ÷ M.Mass

Solving for M.Mass,

                          M.Mass  =  Mass ÷ Mole

Putting values,

                          M.Mass  =  5.0 × 10⁻⁶ g ÷ 8.93 × 10⁻⁸ mol

                          M.Mass =  55.99 g.mol⁻¹ ≈ 56 g.mol⁻¹