#### Answers

* MOLE:- *

*A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly 12 grams of carbon-12 (i.e., 6.023 X 10 ^{23}). This involves the acceptance of two dictates -- the scale of atomic masses and the magnitude of the gram. Both have been established by international agreement. Formerly, the connotation of "mole" was "gram molecular weight." Current usage tends to apply the term "mole" to an amount containing *

*Avogadro 's**number of whatever units are being considered. Thus, it is possible to have a mole of atoms, ions, radicals, electrons, or quanta. This usage makes unnecessary such terms as "gram-atom," "gram-formula weight," etc.*

*All stoichiometry essentially is based on the evaluation of the number of moles of substance. The most common involves the measurement of mass. Thus 25.000 grams of water will contain 25.000/18.015 moles of water, 25.000 grams of sodium will contain 25.000/22.990 moles of sodium. *

*The convenient measurements on gases are pressure, volume, and temperature. Use of the ideal gas law constant R allows direct calculation of the number of moles: n=P V/R T. T is the absolute temperature, R must be chosen in units appropriate for P, V, and T. The acceptance of * ** Avogadro 's law **

*is inherent in this calculation; so too are approximations of the ideal gas.*

**The mole is a unit of measurement for the amount of substance. Moles give us a consistent method to convert between atoms/molecules and grams.**

**The mathematical expression for calculating moles is expressed as:**

**We can express moles in terms of molecular mass, number of atoms/molecules and in terms of volume.**

**· 1 mole of a pure substance has a mass in grams equal to its molecular mass.**-
**1 mole contains the same number of particles as there are in 12g of carbon-12 atoms. This number is called Avogadro’s number and is equal to 6.023 × 10**^{23}particles. -
**1 mole of a gas occupies a volume of: 22.4 litres at S.T.P.**

**For example: 1 mole of sodium atom has mass 23 g. It contains 6.023 × 10**^{23}atoms and occupies 22.4 litres of volume at S.T.P.

**Let us solve a simple numerical to understand this concept in a better way.**

**Numerical:**

**Calculate the number of particles in each of the 46 g of Na atoms.**

**Solution:**

**In this numerical it is desired to find the number of particles in 46 gm of Na.**

**We know that one mole of Na contains 6.023 × 10**^{23}particles.

**Therefore, we will first find the number of moles in 46 gm of Na.**

**We know that 1 mole = 6.022 × 10**^{23}particles.

**Therefore, 2 moles = 2×6.022 × 10**^{23}particles

**= 12.044 × 10**^{23}particles

**Hence, 46 gm of Na contains 12.044 × 10**^{23}particles.

**To be perfect in the mole concept, try to solve more numerical.**

**If you face query, do get back to us. We will be happy to help you.**

**Cheers!**THE MOLE IS A UNIT OF MEASUREMENT FOR THE AMOUNT OF SUBSTANCE.

EXAMPLE : the gram atomic massof carbon is 12. the mass of one atom of carbon has been calculated as 1.9924 *10 raised to -23 g. the number of carbon atoms in 12 g of carbon can be calculated as :

number of carbon atoms = gram atomic mass of carbon / mass of one carbon atom

= 12(g) / 1.9924 * 10 raised to -23 (g) = 6.022 * 10 raised to 23

i hope that you may be kowing about avogadro 's number, the avogadro 's number of particles of any substance are expressed in the form of a term mole. in other words " __ a mole denotes Avogadro 's number of particles __ " pls note that these particles may be any thing atoms, molecules, ions etc......

**hope it helps.... thumb 's up plzzzzzzzzz**

Hi!

One mole of a substance (atoms, molecules, ions, or particles) is that quantity in number having a mass equal to its atomic or molecular mass in grams. One mole of any substance contains 6.022 × 10 ^{ 23 } particles (atoms, molecules, or ions) ** . ** This means that one mole atom of any substance contains 6.022 ×10 ^{ 23 } atoms. Similarly, one mole molecule of any substance contains 6.022 ×10 ^{ 23 } molecules, and one mole ion of any substance contains 6.022 ×10 ^{ 23 } ions. Hence, the mass of a particular substance is fixed.

The number 6.022 × 10 ^{ 23 } is an experimentally obtained value and is known as ** Avogadro’s number ** or ** Avogadro constant ** (represented by ** N ** _{ o } ). It is named after the Italian scientist, Amedeo Avogadro.

Thus, 1 mole of oxygen atoms (O) = 6.022 ×10 ^{ 23 } oxygen atoms.

1 mole of oxygen molecules (O _{ 2 } ) = 6.022 × 10 ^{ 23 } oxygen molecules.

@shubhangi: I hope you would have understood. If your doubt still persists then get back to us.

@others: Very good! Keep up the good work.

This conversation is already closed by Expert