Hello friends, welcome to you in another new article, In this, we will know **what is the mole concept, mole fraction**, etc. In this, to know about the mole completely step by step, then let’s start.

**What is Mole?**

**Mole Concept –**

One mole of a substance is the amount of that substance in which the same number of particles are present as the number of **atoms **in exactly twelve grams of the **carbon-12 **isotope.

The number of particles in one mole of a substance is always the same. Whatever the substance it may be, for the correct determination of this number, the mass of the carbon-12 atom was found by mass spectrometer whose value was found to be** 1.992648×10 ^{-23 }**grams. The mass of one mole of carbon is 12 grams, so the number of atoms in 1 mole of carbon will be as follows:

N = 12g/mol^{12 }C x atom/1.992648×10^{-23} grams per^{12} C

= 6.0221367×10^{23} =** 6.022×10 ^{23} atom/mol**.

This number of particles in 1 mole is called **Avogadro’s number**, and is denoted by *‘N’* or ‘*N _{A}*‘.

**Example**– Number of oxygen atoms in 1 mole =

**6.022×10**

^{23}Hence the number of oxygen atoms in 3 moles = **3x 6.022x10^{23}**

**= 1.811024 atoms **

The given example shows that expressing the number of oxygen atoms in 1.81×10^{24} is a relatively difficult task, so it is very easy to express them in terms of 3 moles of oxygen atoms.

**What is the molar mass?**

**Molar Mass –**

The mass of 1 mole of any substance. It is called its **molar mass,** which is denoted by *“M”*, whose unit is gm/mole.

Molar mass expressed in grams is numerically equal to the molecular mass or mass of the formula. like –

M CO_{2} = Molecular mass of CO_{2}

M CO_{2} = Mass of CO_{2} Formula

M CO_{2} = Molar mass of CO_{2}

M CO_{2} = CO_{2}

= 12+32 = **44 g/mole**

**What is the gram atomic mass?**

**Gram Atomic Mass –**

Gram atomic mass or 1 gram atom is the mass of 6.022×10^{23} atoms of an **element **which is expressed in grams.

**Example **– The gram atomic mass of sodium (Na) or 1 gram atom of sodium (ie 23 grams of Na) is the mass of 1 mole of sodium atoms.

In general, we can express it as follows.

**Gram atomic mass = one gram atom = 1 mole atom = 6.022×10 ^{23} atoms**

**What is the gram molecular mass?**

**Gram Molecular Mass –**

Gram molecular mass, or 1 gram mole, is the mass of 6.022×10^{23} molecules of a substance (element or compound) expressed in grams.

**Example **– The gram molecular mass of CaC0_{3 }or one gram mole (or 100 grams) of CaC0_{3} is 6.022×10^{23} molecules of CaC0_{3} in mass in grams.

In general, we can represent it as follows.

Gram Molecular Mass = One Gram Mole = 1 Mole Molecule = 6.0221023 Molecules

**What is molarity?**

**Molarity **–

The molarity of a substance is the number of grams of molecules that are present in 1 liter of solution, it is called the **molarity **of that substance. The molarity of the substance is denoted by “Mr”. Whose unit is a mole/liter or molar.

VL contains solution = n

Contains 1L solution = n/v

Mr = n/v

n = w/m.pt

Mr = w/mv

w = mass in grams,

m = molecular mass

**w = Mr.m.v /1000**

**What is molality? **

**Molality –**

The molality of a substance is the number of grams of molecules that are present in 1 kg of solvent, it is called the **molality **of that substance. The unit of molality is **mole/kilogram** which is also called **molal**. It is denoted by “Ml”.

Contains Wkg solution = n

Contains 1kg solution = n /W(kg)

Ml = n /W(kg)

n = w /m

**Ml = w /m.W(kg)**

**w = Ml.m.W(gm) /1000**

where Ml = molality of the substance

w = weight of solute

m = molecular weight of the solute

W = weight of solvent

**Normality **–

The normality of a substance is the number of gram equivalents present in one liter of volume. That is called the **normality** of that substance. Which is denoted by ‘N’.

Number of Gram Equivalents = e

VL contains solution = e

Contains 1L solution = e/v

N = e/v

e = w/E

E = equivalent mass of the substance, where w = mass in grams

N = w/E. V[L]

**w = N.E V[ml] /1000 **normal = equivalent/liter

**Relation between Normality and Molarity –**

Let w gram amount of solute is present in one milliliter of solution.

W = E N V (c.c) / 1000

= m Mr. V (c.c) / 1000

Since the amount of solute is the same. Therefore

E N ~~V (cc~~) / ~~1000 ~~= m Mr ~~V (cc)~~ / ~~1000~~

**N/Mr = m/E = x**

x = acidity, basicity, incineration, valency, change in oxidation number, number of cations, number of anions.

m/E = x

E = m/x

Equivalent weight = Molecular mass / Acidity

Example –

HCl = Hydrochloric Acid

E_{HCl} = MHCl /x

E_{HCl} = 1+35.5 / 1

E_{HCl}= **36.5 Ans**

H_{2}SO_{4} = Sulfuric Acid

EH_{2}SO_{4}= MH_{2}SO_{4} / x

= 2+32+64 / 2

= 98/2

**= 49 Ans**

**Stoichiometric Coefficient –**

The coefficients of the formulas of reactants and products in any balanced chemical equation are called** stoichiometric coefficients.** like –

2KClO_{3} ————- 2KCl + 3O_{2}

The stoichiometric coefficient of potassium chlorate is 2 and that of oxygen is 3.

**Parts Per Million (PPM)] –**

1 Million = 10^{6}

When the amount of solute in a solution is very less. So in this case the concentration of the solution is measured in ppm. The number of grams of solute in a million solutions is called **PPM**.

PPM = amount of solute x10^{6}/ volume of solution

For example, if NaCl is 10 PPM, then this statement means that 10 grams of sodium chloride are dissolved in 10^{6} grams of solution.

**What is Mole Fraction? **

**Mole Fraction –**

The ratio of the number of gram molecules of a substance to the total number of gram molecules present in the solution is called the **mole fraction** of that substance.

Therefore it is a ratio of moles, so there is no unit of the mole division. The mole fraction of any substance is denoted by “X”.

Suppose two substances A, B are mixed in an element.

Fraction = His / Total

Mole fraction = its moles / total moles

pressure fraction = its pressure / total pressure

eg – XA = nA / nA+nB

XB = nB/nB+nA

The sum of the mole fractions in any element is equal to one.

XA + XB = 1

According to the ideal gas equation –

PV = nRT

P_{A}V = n_{A}RT ———————- (1)

P_{B}V = n_{B}RT ———————- (2)

P_{T}V = (n_{A}+n_{B})RT ——————- (3)

On dividing equation (1) by equation (3)

P_{A}V / P_{T}V = n_{A}/ n_{A}+n_{B}

P_{A} / P_{T} = X_{A}

Pressure fraction of substance A = Mole fraction of substance A

P_{A} / P_{T} = X_{B}

Pressure fraction of substance B = Mole fraction of substance B

P_{T} = Total Pressure

The pressure fraction of any substance is equal to its mole fraction.

**What is a Limiting Reagent?**

**Limiting Reagent –**

Those reagents which are eliminated first, limit the amount of the product, then such reagents are called** Limiting reagents.**

**Or**

Those reagents are completely reacted in a chemical reaction, and no remaining. So such reagents are called **Limiting reagents**. like –

5 liters of carbon monoxide (CO) react with 2 liters of oxygen (O_{2}) to form carbon dioxide. are called **Limiting reagents**.

_{ }2CO_{2} + O_{2} —————– 2CO_{2}

Law = 2L + 1L

Reaction = 5L + 2L

Left = 1L + 0L

marginal reagent = O_{2}

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