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CBSE - IX - Chemistry - Atoms and Molecules

I haven't really understood mole concept with respect to number? can u explain?

Asked by 2nd March 2013, 5:39 PM
Answered by Expert


The number of molecules in a mole of a substance, approximately 6.0225 × 1023Avogadro's number is commonly used to compute the results of chemical reactions. It allows chemists to determine the exact amounts of substances produced in a given reaction. 
Why we need this number?
Since it is not possible to calculate the weight of particles individually, a collection of such particles called mole is taken for all practical purposes. It was discovered that the number of atoms present in 12g of carbon of 12C isotope is 6.023 x 1023 atoms. This is referred to as Avogadro number after the discoverer Avogadro. A mole of a gas is the amount of a substance containing 6.023 x 1023 particles. It is a basic unit of the amount or quantity of a substance. The substance may be atoms, molecules, ions or group of ions.

Avogadro discovered that under standard conditions of temperature and pressure, (1 atm and 273 K) a sample of gas occupies a volume of 22.4 L.

Answered by Expert 2nd March 2013, 7:45 PM

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