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Introduction 

The term “Mole” was first introduced by Wilhelm Ostwald. The mole concept connects the macroscopic to the molecular or atomic level. As it connects these levels, it allows chemists to weigh and count atoms or molecules. With the help of moles, it becomes easy to measure large objects like elephants by counting and small objects like nails, rice by weight.

Mole

The current definition of one mole is based on the most stable form of carbon, carbon-12. However, it turns out that you can also understand the number of atoms in a mole in terms of a very different natural standard – the nuclear mass of helium. 

  • This approach reveals that Avogadro’s number is 6.022141 × 1023. That’s not a minor difference: In terms of the different definitions, one mole equals not 6.022 × 1023 atoms but 6.02198 × 1023 atoms! Just as using eggs instead of atoms changed our concept of a mole, this discovery would change our understanding of a mole if we adopted it as the official standard for how many molecules are in a mole.

n = N/NA

NA = Avogadro Number

N = Number of moles

N = number of elementary entities

  • For Avogadro’s number to have any significance, the masses of all atoms and molecules in nature must be created equal. All sorts of evidence suggest that this is indeed true. Measurements of the masses of light atoms such as oxygen and hydrogen agree with the calculated mass from their constituent parts. 
  • It’s hard to imagine that hydrogen could have been lighter or heavier than what we find now. But most measurements made over a century ago failed to show any variation in the weights of heavier atoms. They all tended to weigh roughly the same no matter what their atomic number was. 

(moles)(molar mass) → mass

Moles (grams/mole) = grams

(mass/molar mass) → moles

(grams/grams/mole) = grams(mole/grams) = moles

Mole Concept

There is a standard way of expressing amounts of substances in chemistry for use in equations and calculations. It is the mole concept, which assigns a number to the amount of substance present. 

  • This follows on from the atomic mass unit and can be used in all chemical calculations. With the mole concept and molar masses, it is important to know how they work. 
  • The molecular mass and mole concept is not only helpful for carrying out chemical calculations but also provides essential information about how reactants and products are related. 
  • For example, knowing that hydrochloric acid has a mass-to-volume ratio of 35 gives us a way to compare the amounts of HCl and water that react together, whether the amounts are measured in grams or milliliters.

Some Important Formulas

  1. Mass of 1 mole of atoms = Atomic mass in grams
  2. Several moles of atoms = Mass of elements in grams/Relative Atomic Mass
  3. Mass of 1 mole of molecules = Molecular mass in grams
  4. Number of moles of molecule = Mass of the substance in grams/Relative Molecular Mass
  5. Mass of substance containing 1 mole of particles = Molar Mass
  6. Percentage Yield = Atomic Mass of the product obtained/Theoretical mass of product obtained

Molecule:

A molecule is a group of two or more atoms that are chemically bound and held together by gravitational forces.

  • A molecule can be described as the smallest particle of an element or compound that is capable of being an independent being and reflects all the properties of that substance.
  • Atoms of the same element or different elements can form molecules together.

The Indian philosopher Pakodha Katyayama said that usually, particles are present in a common form which gives us different forms of matter. The Greek philosophers Democrats and Lewisipus suggested that when matter divides, there will be a stage when the particles obtained cannot be further distributed. Democrats called these indivisible particles atoms.

Molecules of elements: Molecules of an element are made up of atoms of the same type. Molecules of many elements like Ar, Helium, etc. are formed from just one atom of this element.

Molecules of compounds: Atoms of different elements combine in a certain proportion to form molecules of compounds.

Conclusion 

In this material, we got to learn about the molecular mass and mole concepts and how they are used to solve problems. Apart from it, the main aim of this material was to teach the students to define the mole concept and molar mass easily and conveniently so that they do not face any problems in the exams. With the molecular mass in this material, the understanding of the mole concept gets easier and the equations can be balanced easily now. The mole concept and molar masses class 11 topics will help you understand everything better.