Question

What is the mass of one atom of $\mathrm{carbon}-12$ in grams?

Answer 1

Mole:

• One mole of a substance contains exactly $6.022\times {10}^{23}$ elementary entities. This number is called Avogadro's constant.
• The elementary entities may be an atom, a molecule, an ion, an electron, or any other particle.

Step 1: Molar mass of carbon$\left(\mathrm{C}\right)$:

• Molar mass of carbon$=12\mathrm{g}{\mathrm{mol}}^{-1}$

Step 2: Mass of one atom of $\mathbf{carbon}\mathbf{-}\mathbf{12}$:

• Mass of one mole of $\mathrm{carbon}-12$$=12\mathrm{g}$
• Mass of $6.022\times {10}^{23}$ atoms of $\mathrm{carbon}-12=12\mathrm{g}$
• So, the mass of $1\mathrm{atom}$ of $\mathrm{carbon}-12=\frac{1}{6.022\times {10}^{23}}\times 12\mathrm{g}=1.993\times {10}^{-23}\mathrm{g}$

Therefore, the mass of one atom of $\mathbf{carbon}\mathbf{-}\mathbf{12}$ is $\mathbf{1}\mathbf{.}\mathbf{993}\mathbf{}\mathbf{\times }\mathbf{}{\mathbf{10}}^{\mathbf{-}\mathbf{23}}\mathbf{}\mathbf{g}$.