Molar Mass Calculator Common Compounds Periodic Elements Chemical Formula HCl also known as Hydrochloric Acid Molar Mass of HCl: 36.46 g/mol ElementSymbolAtomsMass % Hydrogen H 1 2.8% Chlorine Cl 1 97.2% 3. Divide Molecular Weight Use the formula moles = grams ÷ molecular weight. In th...