The Mole Concept

Aug 22, 20223 min read

That's exactly , what we are going to do now.

A mole plays a humungous role ( Yup, I had to say that pun somewhere, I thought Why not in the start? (^///^)) in the universe of chemistry, laying the foundation of many theories and concepts... and naturally our academic society made sure this topic is taught in great detail to every highschool kid, and is present in even more immense detail in our exams.

In this blog we will be going through the details, defintions and formulaes of Mole concept and all the topics related to the mole concept

So, Let's start digging

MOLE :- A mole is the amount of a substance that contains as many entities (atoms, molecules or other particles) as there are atoms exactly in 0.012 Kg ( or 12 g) of the carbon -12 isotope

< tbh, this is just a chemically glorified version of how 'a dozen' works, 1 dozen of bananas are 12 entities of bananas... similariy 1 mole of a molecule tells us a particular entities of molecule >

I mole of a molecule constists of 6.02 * 10 ^23 entities of that molecule ( also known as the Avagadro constant

So, let's just imagine you went bananas for bananas and ended up buying 6.02 * 10 ^23 bananas... now you are the proud owner of a mole of bananas

But you might be wondering, why only 6.02 * 10^23 though? Why not 10 lakhs? Why not 22 billlion ? Why were the scientists being so picky with this number?

That is because this seemingly long and complex number actually makes calculations of other quantities easier to solve and remember.

For example :-

1 mole of Carbon atom -- has 6.02 * 10 ^23 atoms -- weighs 12 gram atom mass! ( remember this number from somewhere else? ... You don't ? Don't fret. We will be discussing it soon )

So when someone asks "Hey, could you pass me a mole of Sodium " , You can go " Sure" and hand over 23 grams of sodium... An everyday conversation you make with your friends right?

Let's clear some basics before me move any forward

* Atomic Mass :- Mass of one atom is called Atomic mass

Unit :- a.m.u

Egs -- Atomic Mass of Hydrogen --> 1 a.m.u

*Molecular Mass :- Mass of one molecule is molecular mass

Egs:- Molecular Mass of H20 --> 18 a.m.u

and 1 atomic mass unit ( a.m.u) = 1/12 × Mass of 1 atom of Carbon - 12

Which in colloquial terms is

* Relative Atomic Mass (R.A.M)

One thing to notice here is that both numerator and denominator are of the same unit which is a.m.u, hence this is a unitless quantity

Simplification of the above gives us = Mass of 1 atom

Egs:- R.A.M of H = 1

O = 16

( The same can be applied as Relative Molecular Mass (R.M.M) for molecules)

Now that the basics of mass and atoms are covered, let's actually start

(I) Mole concept in terms of number

Whenever we are given number of entities

(II) Mole concept in terms of Moles

Molar mass of any substance is numerically equal to atomic mass or molecular mass

Unit of Molar Mass = gram

This is also known as Gram atomic mass or gram molecular mass

(III) Mole concept in terms of Volume

For an ideal gas ,

PV = nRT

* P = Pressure of gas in atom

( 1 atm = 76cm of Hg

= 760mm og Hg

= 760 torr

1 bar = 0.987 atm)

* V = Volume of gas in lit (volume of container)

* n = Number of moles

* R = 0.0821 lit atm / mole [ aka universal gas constant]

* T = temperature in 'Kelvin' scale

> at 273 K, 1 atm pressure, if n = 1 mole

V = 22.4 lit

Hence, Volume occupied by 1 mole of gas at STP is 22.4 called Gram molecular volume

In conclusion,

(IV) Relation between Density and Moles

Density of Gas:-

Another tiny subtopic related to Density is -- Relative Density

Hence as M of H2 = 2

Relative density = Mass of gas /2

(R.D is also known as Vapour Density )

VD gas * 2 = M gas

Okay, this was all the basics of the Mole concept, The topics and concepts we read from here are the ones which have their core related to Mole concept.

Mole Percentage and Weight Percentage

In a mixture of A,B and C