Question

Solve problem:

Calculate the number of moles and molecules of acetic acid present in 22 g of it.

Answer 1

Given: Mass of acetic acid = 22 g

To find: The number of moles and molecules of acetic acid

Formulae:

1. Number of moles =`"Mass of a substance"/ "Molar mass of a substance"`
2. Number of molecules = Number of moles × Avogadro's constant

Calculation: Mass of acetic acid = 22 g
Molecular mass of acetic acid, CH₃COOH
= (2 × Average atomic mass of C) + (4 × Average atomic mass of H) + (2 × Average atomic mass of O)
= (2 × 12 u) + (4 × 1 u) + (2 × 16 u)
= 60 u
∴ Molar mass of acetic acid = 60 g mol^–1
Number of moles = `"Mass of a substance"/"Molar mass of a substance"=(22"g")/(60"g  mol"^-1)` = 0.367 mol
Now,
Number of molecules of acetic acid = Number of moles × Avogadro's constant
= 0.367 mol × 6.022 × 10²³ molecules/mol
= 2.210 × 10²³ molecules

1. Number of moles = 0.367 mol
2. Number of molecules of acetic acid = 2.210 × 10²³ molecules