Relative molar mass is defined as the smallest mass unit of a compound with one-twelfth of the mass of one carbon – 12 atom. The standard unit for this is g mol−1.
Mathematically, the defining equation of molar mass is
Molar mass = mass/mole = g/mol
Oxalic acid= HOOCCOOH
Chemical formula of oxalic acid= C2H2O4
Molar mass = 12 x 2 + 1 x 2 + 16 x 4
= 24 + 2 + 64
= 26 + 64
= 90 g/mol
The molar mass of oxalic acid is 90 g/mol.