write some easy small points about mole concept
Answers
Mole:
One mole is defined as the amount of substance of a system which contains as many entities like, atoms, molecules and ions as there are atoms in 12 grams of carbon - 12".
Later it was found that one gram atom of any substance contains as many atoms as are present in 1 gram atom of carbon12 isotope.
The value of this number is found to be 6.023X10²³ and this is called as Avogadro's number.
Avogadro number:
The number of the particles present in one mole of any substance is equal to 6.022x10²³. This is called avogadro’s number or avogadro’s constant.
It is represented by N.
Number of particles in 1 mole:
1 mole of hydrogen atoms represents 6.022 × 10²³ hydrogen atoms.
1 mole of hydrogen molecules represents 6.022 × 10²³ hydrogen molecules.
1 mole of water molecules represents 6.022 × 10²³ water molecules.
Importance of mole concept and Avogadro's number
mole concept and Avogadro's number help in the calculations in so many ways. They are,
i) Helps in the calculation of actual mass of single atom of an element or single molecule of a substance
Examples
a) Find the mass of 1 atom of nitrogen
Solution - 1 mole of nitrogen = 14g = 6.023x10²³ atoms
Mass of 6.023x1023 atoms = 14g
Mass of 1 atom of nitrogen = 14 /6.023x10²³
= 2.32 X 10-23 g.
b) Calculate the mass of a molecule of CO
Solution -1 mole of CO= 28g
1 mole CO = 6.023x10²³ molecules
Therefore mass of 6.023x10²³ molecules of CO = 28g
Mass of 1 molecule of CO = 28/6.023x10²³
= 4.64 X10⁻²³ g
ii) Helps in the calculation of number of atoms or molecules present in a given mass of element or compound.
Example
Calculate the number of water molecules contained in a drop of water weighing 0.06g ?
Ans: 18g of water = 1 mole
0.06 g = ?
= 0.06/18 = 3.33 X 10-3 mole of water
1 mole of water contains - 6.022X10²³ molecules of water
3.33 X 10-3 mole of water contains -----?
= 6.022X10²³ X 3.33 X 10⁻³
= 2 X 10²⁰ molecule of water
∴ 0.06g of water contains 2 X 10²⁰ molecules of water.
iii) Helps in the calculation of number of molecules present in a given volume of the gas under given conditions.
Example
Calculate the number of molecules present in 600c.c of NH3 at S.T.P.
Hint - This problem can be solved by using mole concept.
Solution - 1 mole of NH3 = 6.023 X 10²³ molecules = 22400 c.c at STP
That is 22400 c.c of NH3 at STP contains 6.023 X 10²³ molecules
600 c.c of NH3 at STP contains = 6.023 x10²³/22400 X 600 = 0.161 X 10²³ molecules
Avogadro's number, number of particles and moles - conversion formulae
Number of moles (n) = Given number of particles (N) / Avogadro number (N₀)
Answer:
1 MOLE IS THE AMOUNT OF SUBSTANCE EQUAL TO MOLECULAR MASS OF THAT SUBSTANCE.
Explanation:
For example:
carbon have molecular mass= 12 g/mole
so its 1 mole = 12 g of carbon.
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