The Mole & Calculations

Relative formula mass, the mole, reacting masses, concentrations and gas volumes.

Chemical calculations use the mole to connect masses, volumes and numbers of particles.

Relative formula mass and the mole

$n = \frac{m}{M_r} \qquad n = c \times V \qquad n = \frac{V_\text{gas}}{24}\ (\text{dm}^3\text{ at rtp})$

Worked example. How many moles in $50$ g of CaCO₃? $M_r = 40 + 12 + 48 = 100$ , so $n = \dfrac{50}{100} = 0.5$ mol.

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Relative formula mass and the mole

n = \frac{m}{M_r} \qquad n = c \times V \qquad n = \frac{V_\text{gas}}{24}\ (\text{dm}^3\text{ at rtp})

Worked example. How many moles in

50

g of CaCO₃?

M_r = 40 + 12 + 48 = 100

, so

n = \dfrac{50}{100} = 0.5

mol.