Question

what is mole concept ? calculate the number of molecules in 45g of water.

Answer 1

The mole is the unit of measurement for amount of substance in the International System of Units (SI). The unit is defined as the amount or sample of a chemical substance that contains as many constitutive particles, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 gramsof carbon-12 (12C), the isotope of carbon with standard atomic weight 12 by definition. This number is expressed by the Avogadro constant, which has a value of approximately 6.022140857×1023 mol−1. The mole is an SI base unit, with the unit symbol mol.

Given mass = 45g
Molar mass of H2O = 2+16 = 18g

Moles = Given mass/Molar mass
 = 45/18 = 2.5moles

No of molecule in 1 mole = 6.022*1023​​
No of molecue in 2.5 mole = 2.5*6.022*1023​​
 = 1.5055*1024

Answer 2

The mole is the unit of measurement for amount of substance in the International System of Units (SI). The unit is defined as the amount or sample of a chemical substance that contains as many constitutive particles, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 gramsof carbon-12 (12C), the isotope of carbon with standard atomic weight 12 by definition. This number is expressed by the Avogadro constant, which has a value of approximately 6.022140857×1023 mol−1. The mole is an SI base unit, with the unit symbol mol.

Given mass = 45g
Molar mass of H2O = 2+16 = 18g

Moles = Given mass/Molar mass
 = 45/18 = 2.5moles

No of molecule in 1 mole = 6.022*1023​​
No of molecue in 2.5 mole = 2.5*6.022*1023​​
 = 1.5055*1024