How many carbon atoms are there in a diamond (pure carbon) with a mass of "48" mg?

              3.47 × 10²³ C atoms

Solution:

Data Given:

                 Mass of Diamond  =  48 mg  =  0.048 g

                 M.Mass of Diamond  =  12.01 g.mol⁻¹ (as it is purely Carbon)

Step 1: Calculate Moles of Diamond as,

                 Moles  =  Mass ÷ M.Mass

Putting values,

                 Moles  =  0.048 g ÷ 12.01 g.mol⁻¹

                 Moles  =  0.576 mol

Step 2: Calculate number of Carbon atoms,

As 1 mole of any substance contains 6.022 × 10²³ particles (Avogadro's Number) then the relation for Moles and Number of Carbon atoms can be written as,

                 Moles  =  Number of C Atoms ÷ 6.022 × 10²³ Atoms.mol⁻¹

Solving for Number of C atoms,

                 Number of C atoms  =  Moles × 6.022 × 10²³ Atoms.mol⁻¹

Putting value of moles,

                 Number of C atoms  =  0.576 mol × 6.022 × 10²³ Atoms.mol⁻¹

                 Number of C atoms =  3.47 × 10²³ C atoms

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante