Question

What is a gram molecule? And gram equivalent? Give an example

Answer 1

Gram molecule:

• “A gram molecule can be defined as the number of grams of a substance which is the same as the relative molecular mass of that particular substance.”
• For example, One gram-molecule of water is 18 grams $({\mathrm{H}}_2\mathrm{O}=1+1+16=18\mathrm{g})$.

Gram equivalent:

• “Equivalent mass is equal to the molecular/atomic mass divided by the number of electrons involved in the reaction per molecule/atom/ion.”
• It is given by: $\mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{Element}=\frac{\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Element}}{\mathrm{Valency}}$
• For example, the equivalent mass of copper is shown below:

$$\begin{gathered} \mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{Cu}=\frac{\mathrm{Atomic}\mathrm{mass}\mathrm{of}\mathrm{Cu}}{\mathrm{Valency}} \\ \mathrm{Equivalent}\mathrm{mass}\mathrm{of}\mathrm{Cu}=\frac{63.5\mathrm{g}{\mathrm{mol}}^{-1}}{1}=63.5\mathrm{g}{\mathrm{eq}}^{-1} \end{gathered}$$