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Mole
In the beginning, he hypothesized that the true character of a substance not only depends on the type of substance but also on the quantity of the type of substance or atom. Then after years of research, he came up with a definition for mole as the amount of substance containing the same number of distinct entities (atoms, molecules, ions, etc.) as the number of atoms in a sample of pure 12C weighing exactly 12 g. (Avogadro number) or a mole is defined as the amount of a substance that contains exactly 6.02214076 * 1023 ‘elementary entities’ of the given substance.
The number of entities composing a mole has been determined to be 6.022×1023, a fundamental constant named Avogadro’s number (NA) or the Avogadro constant.
Mole is convenient in many ways. Let’s take a look at an example. To express amounts of reactants and products of chemical reactions, the chemical equation 2H2 + O2 → 2H2O can be interpreted to mean that for each 2 mol hydrogen (H2) and 1 mol dioxygen (O2) that react 2 mol of water (H2O) form.
Mole Concept
The true definition of the mole concept is that it is a convenient method for measuring any substance. For instance, in chemistry, if asked to calculate the number of molecules, it becomes difficult, but with the mole concept, it has become easier, simpler methods of quantizing.
What Is Molar Mass?
The molar mass of a substance is the mass of 1 mole of that substance. Number. For most practical purposes, the magnitude of molar mass is numerically the same as that of the mean mass of one molecule, expressed in Daltons or units of grams per mole (g/mol).
The molar mass of an element, for instance, let’s take carbon A mole of 12C weighs 12 g; hence its molar mass is 12 g/mol.
Before moving further, these are some basic
Formulae based on the mole concept;
The number of moles in a given element or compound can be calculated by dividing the total mass of the compound by the molar mass of the element or compound, as described by the following formula.
Number of moles=mass of the given sample/ molar mass
The total number of atoms or molecules in a sample can be calculated by multiplying the number of moles with the Avogadro constant. This formula can be written as:
number of atoms or molecules=Number of moles × 6.022*1023
The relationship between the atomic mass unit (amu) and the gram is represented as
1 amu = (1gram)/(6.022*1023) = 1.66*10-24 grams
Molar Concentrations;
1.Molarity(M): The molar unit is probably the most commonly used chemical unit of measurement. Molarity is the number of moles of a solute dissolved in a litre of solution. Represented by “M”.
M=n/V
2.Molality(m): A molality is the number of moles of solute dissolved in one kilogram of solvent. Never confuse morality and morality. Molality is represented by a small “m,” whereas molarity is represented by an uppercase “M.”
m=moles of the solute /weight of solvent in g
3.Normality(N): The number of gram equivalents of solute in one litre of solution. It is represented as “N”.
N=Gram equivalent of solute /Volume of solution in L
What is Mole Fraction?
The mole fraction of a substance in a mixture is the number of moles of the compound in one sample of the given mixture, divided by the total number of moles of all compound components.
Solved Examples:
- Calculate the molar mass of Ammonium Sulphate. [(NH4)2SO4]
Ans: Therefore, molecular mass =14+1×4×2+32+(16×4)
= 36+32+64
=132amu.
- How many moles are present in 200g of NaOH
Ans: The mass of 1 mole of NaOH = 23+16+1=40
Therefore, 200g is 200/40=5
Five moles are present.
Conclusion
We can conclude by saying that, with the help of the mole concept and its formulae, many calculations which seemed impossible were easily calculated. The Mole concept’s true meaning lies in how it has turned out to be a benefit for counting the number of molecules or be it calculating the molar mass. We have also discussed some stoichiometric terms deeper into the subject, which will come in handy while calculating the molar concentration. The mole concept covers half of the chemistry.
