Define gram molecular mass.
Gram molecular mass:
Molecular mass of a substance expressed in grams is called gram molecular mass.
Mass of one mole of water = Molecular mass of H2O
= 2 x 1.008 + 16
$\therefore$ 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