Question

How do you calculate $1\mathrm{amu}$in grams using the ${\mathrm{C}}_{12}$ atom?

Answer 1

Step 1: $1\mathrm{amu}$

The mass of one carbon atom which is having the atomic number 12 is $12\mathrm{amu}$.

According to the Avogadro law, one mole of the substance has the Avogadro number of molecules that is $6.023\times {10}^{23}$ atoms.

So, $6.023\times {10}^{23}$ carbon atoms will have the mass of $12\mathrm{g}$.

The mass in grams for 1 unit of the substance will be

Therefore,

$$\begin{gathered} 1\mathrm{amu}=\frac{12\mathrm{g}}{6.023\times {10}^{23}} \\ 1\mathrm{amu}=1.661\times {10}^{-24}\mathrm{g} \end{gathered}$$

Hence, the value of $1\mathrm{amu}$ is $1.662\times {10}^{-24}g$.