what is the formula to calculate equivalent weight?
Equivalent weights may be calculated from molar masses if the chemistry of the substance is well known: sulfuric acid has a molar mass of 98.078(5) g mol−1, and supplies two moles of hydrogen ions per mole of sulfuric acid, so its equivalent weight is 98.078(5) g mol−1/2 eq mol−1 = 49.039(3) g eq−1.