Question

How do you calculate the number of moles? Explain with example.

Answer 1

Calculating the number of moles:

• Mole is referred to as a measure or base unit of the amount of substance present in a given particle or substance, which can be any type of species, e.g.
• 1 mole is a number equal to $6.022\mathrm{x}{10}^{23}$ particles, also known as the Avogadro’s constant.
• To calculate the number of moles of any substance in the sample, we simply divide the given weight of the substance by its molar mass.
• The formula for the number of moles is, therefore:

$\mathrm{n}=\frac{\text{mass of substance}}{\text{mass of one mole}}$

• Mathematically, $\mathrm{n}=\frac{\mathrm{m}}{\mathrm{M}}$ (Where, n = The number of moles, m = The given mass, and M = The molar mass)

Example: Calculating how many moles of sodium chloride are present in a sample that has a mass of 1.17g;

• Here, the molar mass of Sodium Chloride = $23+35.5=58.5\mathrm{g}$
• So, $\mathrm{No}.\mathrm{of}\mathrm{moles}=\frac{\mathrm{Mass}\mathrm{of}\mathrm{NaCl}}{\mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{NaCl}}$

$$\begin{gathered} =1.17/58.5 \\ =0.02\mathrm{mol} \end{gathered}$$

Hence, we can calculate the number of moles by using the above-mentioned formula as;$\mathrm{n}=\frac{\mathrm{m}}{\mathrm{M}}$.