15.1 The Mole and Amount of Substance

Definition: The Mole

• Amount of substance containing a number of particles equal to the Avogadro Constant ($N_A$)

Definition: Avogadro Constant ( $N_A$)

• Number of particles per unit amount of substance
• Is equal to $6.02\times 10^{23}$

Calculating Number of Moles of Substance

You can calculate the number of moles ($n$) using either the number of molecules ($N$) or the mass of the substance ($m$): $n=\frac{N}{N_A}$ $n=\frac{m}{M_r}$

Where:

• $N$: Total number of particles.
• $N_A$: Avogadro’s constant ($6.02\times 10^{23}$).
• $m$: Total mass of substance (g or kg).
• $M_r$: Molar mass (mass of one mole of substance in $\mathrm{gmo}{\mathrm{l}}^{-1}$ or $\mathrm{kgmo}{\mathrm{l}}^{-1}$).