Question

What is the molecular weight of $\mathrm{NaOH}$?

Answer 1

Step1. Molecular weight

• Molecular weight is the sum of atomic weight, measured in amu.
• The mass of one carbon atom is equal to the atomic mass unit (formerly abbreviated as 'amu,' but now spelled as 'u' – unified mass) according to the latest IUPAC recommendation.

Step2. The formula for the molecular weight of $\mathrm{NaOH}$

The molecular weight of $\mathrm{NaOH}$=$\mathrm{The}\mathrm{atomic}\mathrm{weight}\mathrm{of}\mathrm{Na}+\mathrm{The}\mathrm{atomic}\mathrm{weight}\mathrm{of}\mathrm{O}+\mathrm{The}\mathrm{atomic}\mathrm{weight}\mathrm{of}\mathrm{H}$

Step3. Calculation of molecular weight of $\mathrm{NaOH}$

The molecular weight of $\mathrm{NaOH}$

$$\begin{gathered} =\left(22.990+15.999+1.008\right)\text{u} \\ =39.997\text{u} \\ \approx 40\text{u} \end{gathered}$$

Hence, the molecular weight of $\mathrm{NaOH}$ is $40\hspace{0.17em}\text{u}$.