Biology, asked by shreyansh8151, 1 year ago

Molecular mass and the the concept mole

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Answered by Anonymous
5
mole concept and Molecular mass

one mole is the amount of a substance that contains as many particles as there or atomic in externally 12 gram or 0.012 kg of the 12c isotope
the mass of 1 mole of substance is grammas is called them its molar mass
Answered by roshan30
1
Molecular Mass


The molecular mass of a substance is the relative mass of its molecule as compared with the mass of a 12C atom taken as 12-units. It indicates the number of times; one molecule of the substance is heavier than

atom.

Calculation of Molecular Mass


Molecular mass is equal to sum of the atomic masses of all atoms present in one molecule of the substance.Example: H2OMass of H atom = 1Mass of 2H atoms = 2Mass of O atom = 16Molecular mass = 2 + 16 = 18g

Relative Molecular Mass


Relative molecular mass or RMM is the molecular weight of an element or a compound. It is the number of times one molecule of the substance is heavier than 1/12 the mass of an atom of carbon (12C).



Gram Molecular Mass


Molecular mass expressed in grams is numerically equal to gram molecular mass of the substance.Molecular mass of O2 = 32Gram molecular mass of O2 = 32gGram molecular mass is the relative molecular mass expressed in grams.Note that relative atomic mass is a ratio and has no units while gram molecular mass and gram atomic mass are expressed in grams.

Mole Concept


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 1023atoms. 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.


Molar Volume


One mole of any gas at STP will have a volume of 22.4 L. This is called molar volume.

The molar volume [22.4 L at STP] plays a vital role in stoichiometric calculations because it is the link between volume and mass in reactions involving gases.

Relationship Between Gram Molecular Weight and Gram Molecular Volume


Gram molecular weight (GMW) or mole is the relative molecular mass of a substance expressed in grams. It is also called gram molecular weight of that element.

Gram molecular volume (GMV) or molar volume is the volume occupied by one-gram molecular weight of a gas at STP (Standard temperature and pressure).

All gases of equal volumes contain same number of molecules under the same conditions of temperature and pressure. Equal number of molecules of different gases will occupy equal volumes under the same conditions of temperature and pressure.

One mole of gas = 6.023 x 1023molecules

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