Calculate the number of molecules in 4 g of oxygen.

Mole concept provides a relationship between number of particles and their mass. Thus it is possible to calculate the number of particles in a given mass.

Molar mass of oxygen(O2) = 32g


Given mass of the oxygen = 4g


As we know that, Number of moles = G mass of an element/molar mass of an element


Hence, Number of moles of oxygen = 4g/32g = 0.12 moles


Since 1 mol of oxygen contains 6.022 × 1023 molecules.


Therefore, 1.5 mol of oxygen contains = 6.022 × 1023 molecules / mol × 0.12mol = 7.528 × 1022 molecules of oxygen.


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