Question

Which has more number of atoms, $100$ grams of Sodium or $100$ grams of Iron (given, atomic mass of $\mathrm{Na}$ $=23u$, $\mathrm{Fe}$ $=56u$)?

Answer 1

Step 1- Finding number of moles of Sodium-

Number of moles =$\frac{\mathrm{Given}\mathrm{mass}}{\mathrm{Molar}\mathrm{mass}}$

=$\frac{100\mathrm{g}}{23\mathrm{g}{\mathrm{mol}}^{-1}}$

=$4.345\mathrm{mol}$

Step 2- Finding number of atoms of Sodium-

Number of atoms= $4.35\mathrm{x}\mathrm{Avogadro}\text{'}\mathrm{s}\mathrm{number}$

=$4.35x6.022x{10}^{23}\mathrm{atoms}$

= $2.61\mathrm{x}{10}^{24}\mathrm{atoms}$

Step 3- Finding number of moles of Iron-

Number of moles= $\frac{100\mathrm{g}}{56\mathrm{g}{\mathrm{mol}}^{-1}}$

=$1.78$ moles.

Step 4- Finding number of moles of Iron-

Number of atoms= $1.78x6.022x{10}^{23}$

= $1.07x{10}^{24}$ atoms

Thus, $100$ grams of Sodium (Na) has more number of atoms.