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,

                          Number of Moles  =  Number of Particles ÷ 6.022 × 10²³

Putting values,

                          Number of Moles  =  5.38 × 10¹⁶ Molecules ÷ 6.022 × 10²³

                          Number of 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