Question

atoms and molecules class 9 all formulas of chapter​

Answer 1

Answer:

The molecular formula is the expression of the number of atoms of each element in one molecule of a compound. The molecular formula definition is the formula showing the actual number of each atom in a molecule.

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Answer 2

SOME USEFUL FORMULAE

Number of moles of atoms =Mathematically,

n=$\frac{m}{M}$  

Where ’n’ is the number of moles, ‘m’ is the given mass and ‘M’ is the molar mass.

Here is a small map that can help you to relate number of moles, volume and mass of a substance.

Example: How many moles are in 25.0 grams of water?

Solution:  

In order to find the number of moles, we will have to use the following formula

n=mM

n=mM

Molar Mass, M, of H2O = 18.0 gm/mol

Given mass, m, of H2O = 25.0 gm

So, n = 25.0 (gm) / 18.0 (gm/mol)

Number of moles, n = 1.39 mol

Number of moles =Number of moles = Mass of substance / Mass of one mole

Number of moles of molecules = Avogadro's number is used to calculate the number of molecules present in any given mass of the compound, in which 1 mole of the molecule is equal to 6.023×$10^{23}$  

of numbers of molecules.

(i) 1 mole of molecules = Gram molecular mass.

(ii) 1 mole of molecules = 6.023 × $10^{23}$ molecules.

(iii) Gram molecular mass = 6.023 ×$10^{23}$molecules.