Gram molecular mass:

Molecular mass of a substance expressed in grams is called gram molecular mass.

Examples:

Mass of one mole of water = Molecular mass of H₂O

= 2 x 1.008 + 16

=18.016 g

$\therefore$ Gram molecular mass of H₂O = 18.016g

Molecular mass of C₆H₁₂O₆ = 6 x 12 +12 x 1.008 + 16 x 6

= 180.096 g

$\therefore$ Gram molecular mass of C₆H₁₂O₆ = 180.096 g