Calculate the molecular and molar masses of the following:- NaOH, H3PO4, Na2SO4.

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Solution

Dear Student,
Molecular mass is a number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom, which is taken to have a mass of 12. Its unit is u.

The molar mass of a particular substance is the mass of one mole of that substance. It is equal to molecular mass of the substance for one mole of substance. Its unit is gram per mole.
1.) NaOH
molecular mass of NaOH = mass of Na atom + mass of O atom + mass of hydrogen atom
= 22.989769 u + 15.999 u + 1.00784 u = 39.996609 u
molar mass of NaOH = 39.99609 gm/mol
2.) H₃PO₄
molecular mass of H₃PO₄ = 3 x mass of hydrogen atom + mass of phosphorus atom + 4 x mass of oxygen atom
= 3 x 1.00784 u + 30.973762 u + 4 x 15.999 u = 97.993282 u
molar mass of H₃PO₄ = 97.993282 gm/mol
3.) Na₂SO₄
molecular mass of Na₂SO₄= 2 x mass of sodium atom + mass of sulphur atom + 4 x mass of oxygen atom
= 2 x 22.989769 u + 32.065 u + 4 x 15.999 u = 142.040538 u
molar mass of Na₂SO₄ = 142.040538 gm/mol

Regards

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