How to calculate the number of moles

calculating the number of moles - chemistry

How to calculate the number of moles

The number of mole is mass divided by molar mass

  • Knowing the number of moles allows you to calculate the number of atoms if you are dealing with chemical compounds.
  • Moles are very useful, they allow chemists to use chemical equations to determine the mass of reactants and products.

Read about Avogadro Constant

Example

How many moles in 1000 g of C12H22O11 (sugar)?

Solution:

Step 1: Molar mass = 12(12.01) + 22(1.008) + 11(16) = 342.296g/mol

Step 2: n = m/mm = 1000g/342.296g per mol = 2.92 moles (rounded)

Atomic mass from the periodic table

Elements Symbol Atomic Mass
Hydrogen H 1.00794
Carbon C 12.0107
Oxygen O 15.9994

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