What is the formula that links moles, mass and Mr?

mass = moles x Mr

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mass = moles x Mr


Rearrange the above formula to get moles by itself.

moles = mass ÷ Mr

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What is a mole?

A mole is a unit of measure (like a mile, hour, or litre).


1 mole of a substance is the amount of that substance that contains 6.02 x 1023 particles (e.g. atoms or molecules).

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What is Avogadro’s constant?

The number of particles (e.g. atoms / molecules / ions) in 1 mole of a given substance. The value of the constant is 6.02 x 1023.



  • 1 mole of carbon is exactly 6.02 x 1023 atoms of carbon.
  • 1 mole of hydrochloric acid (HCl) is exactly 6.02 x 1023 molecules of HCl.

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