Definition
The mole (symbol: mol) is the SI unit of quantity of substance. One mole of a substance contains exactly 6.022 140 76 × 1023 elementary units, for example, atoms, molecules, or ions. This number is called the Avogadro number: 6,022 140 76 × 1023. The Avogadro constant (Avogadro constant) NA, on the other hand, is denoted as 6.022 140 76 × 1023 mol-1 is defined. Thus, one mole of water, sugar, or acetaminophen is always equal to Avogadro’s number. One millimole (mmol) corresponds to one thousandth of a mole, one micromole (µmol) corresponds to one millionth of a mole, and one nanomole (nmol) corresponds to one billionth of a mole.
Calculation of the number of molecules
How many molecules are there in 5 moles of water? Number = 5 x Avogadro number = 5 x 6.022 × 1023 = 3.011 × 1024
Number of elements in a compound
Paracetamol (C8H9NO2) consists of:
- 8 carbon atoms (C)
- 9 hydrogen atoms (H)
- 1 nitrogen atom (N)
- 2 oxygen atoms (O)
1 mol of paracetamol is equivalent to:
- 8 moles of carbon
- 9 mol hydrogen
- 1 mol nitrogen
- 2 moles oxygen
Reference to molecular mass
Paracetamol has a molecular mass of 151.16. 1 mol of paracetamol is exactly 151.16 g. The dosage of minerals and trace elements is sometimes expressed in units of moles.
How many milligrams of magnesium equals 7.5 mmol?
For example, effervescent tablets containing 7.5 mmol of magnesium are commercially available. How many milligrams (mg) does this equal?
- Magnesium has the atomic mass 24.3 u
- 1 mol magnesium = 24.3 g
- 1 mmol magnesium = 24.3 mg
- 7.5 mmol magnesium = 7.5 x 24.3 mg = 182.25 mg magnesium
Example potassium
Potassium has the atomic mass 39.1 u.
How many molecules are in one kilogram of table sugar?
Household sugar consists of sucrose (C12H22O11, 342.3 g/mol)
- 1 mol sucrose = 342.3 g
- 1 g sucrose = 0.002921 mol
- 1 kg sucrose = 2.921 mol
- 1 kg sucrose = 2.921 mol x 6.022 × 1023 mol-1 = 1.759 x 1024 molecules
