question_answer 28)

                  Calculate the number of atoms in 39.4 g gold. Molar mass of gold is 197 g \[mol{{e}^{-1}}\].

Answer:

                  No. of atoms in m gram                 \[\text{=}\,\frac{\text{Avogadro }\!\!'\!\!\text{ s}\,\,\text{number}\,\times \,\text{m}\,}{\text{mole}\,\,\,\text{mass}}\]                 \[\therefore \] No. of atoms is 39.4 g gold                 \[=\,\frac{6.023\,\times \,{{10}^{23}}\times \,39.4}{197}\,\,=1.2\,\,\times \,{{10}^{23}}\]