How Do You Calculate the Weight of One-Mole Water (Molar Weight)

Q. How do you calculate the weight of one mole of water (molar weight)? 

Answer: The molar mass of a chemical compound is equal to the mass of the sample divided by the molecular weight of the sample. In order to calculate the molar mass, one must take into account the mass differences between isotopes of the substance.

If one molecule has an average mass of one dalton, one dalton has an average mass of two daltons, and so on and so forth, then one dalton has an average mass of one molecular mass (for all practical purposes). H2O is the molecular formula for water.    

• Water constitutes one molecule of oxygen and two molecules of hydrogen.
• The molar weight of a hydrogen atom is 1g.
• The molar weight of oxygen is 16g.
• Weight of two moles of hydrogen = 2g per mole.
• By the additional reaction of 2 moles of hydrogen and one mole of oxygen, we get one mole of water.

• • Weight of two hydrogen atoms = 2*1g/mole = 2g/mol.

• Mass of one mole of water = 2g/mole(H2) + 16g/mole(O) = 18g/mole.