Mole concept, mole fraction, definitions, molar mass

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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/mol12 C x atom/1.992648×10-23 grams per12 C

= 6.0221367×1023 = 6.022×1023 atom/mol.

This number of particles in 1 mole is called Avogadro’s number, and is denoted by ‘N’ or ‘NA‘. Example – Number of oxygen atoms in 1 mole = 6.022×1023

Hence the number of oxygen atoms in 3 moles = 3x6.022x1023

= 1.811024 atoms

what is mole concept, mole fraction
What is the mole concept,

The given example shows that expressing the number of oxygen atoms in 1.81×1024 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 –

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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 CO2 = Molecular mass of CO2

M CO2 = Mass of CO2 Formula

M CO2 = Molar mass of CO2

M CO2 = CO2

= 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 6.022×1023 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 = 6.022×1023 atoms

What is the gram molecular mass?

Gram Molecular Mass –

Gram molecular mass, or 1 gram mole, is the mass of 6.022×1023 molecules of a substance (element or compound) expressed in grams.

Example – The gram molecular mass of CaC03 or one gram mole (or 100 grams) of CaC03 is 6.022×1023 molecules of CaC03 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 –

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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

EHCl = MHCl /x

EHCl = 1+35.5 / 1

EHCl= 36.5 Ans

H2SO4 = Sulfuric Acid

EH2SO4= MH2SO4 / 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 –

2KClO3 ————- 2KCl + 3O2

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

Parts Per Million (PPM)] –

1 Million = 106

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.

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PPM = amount of solute x106/ volume of solution

For example, if NaCl is 10 PPM, then this statement means that 10 grams of sodium chloride are dissolved in 106 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

PAV = nART ———————- (1)

PBV = nBRT ———————- (2)

PTV = (nA+nB)RT ——————- (3)

On dividing equation (1) by equation (3)

PAV / PTV = nA/ nA+nB

     PA / PT = XA

Pressure fraction of substance A = Mole fraction of substance A

PA / PT = XB

Pressure fraction of substance B = Mole fraction of substance B

PT = 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 (O2) to form carbon dioxide. are called Limiting reagents.

    2CO2 + O2 —————– 2CO2

Law = 2L + 1L

Reaction = 5L + 2L

Left = 1L + 0L

marginal reagent = O2

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