Hydrochloric Acid

• Aqueous solution of hydrogen chloride (HCl) gas is called hydrochloric acid. Hydrochloric acid is a very strong acid. It hydrolyzes in water into H+ and Cl﹣. The pKa of hydrochloric acid is -6.0.
• Hydrochloric acid (HCl) is a strong, colorless, and highly corrosive inorganic acid known for its pungent odor and wide-ranging applications. 
• Chemically, it is a diatomic molecule composed of hydrogen and chlorine atoms bound by a polar covalent bond, with a molar mass of 36.46 g/mol. 
• In its gaseous form, HCl is a colorless gas, but when dissolved in water, it forms a clear, highly acidic aqueous solution. The acid fully dissociates in water, producing hydronium (H₃O⁺) and chloride (Cl⁻) ions, which results in a low pH (e.g., ~0 for a 1 M solution). 
• Its physical properties, such as density (~1.19 g/cm³ for 38% HCl) and boiling point (~108°C for 20% HCl), vary with concentration. 
• HCl is highly soluble in water, releasing significant heat during dissolution, and is also soluble in polar solvents like methanol. 
• Naturally, it occurs in the human stomach, where it aids digestion by denaturing proteins, and in volcanic emissions as a gas that can contribute to acidic rain.
• The molecular structure of HCl is simple yet significant. It consists of a linear diatomic molecule with a bond length of approximately 127.4 picometers. The bond is polar due to chlorine’s higher electronegativity (3.16) compared to hydrogen (2.20), creating a dipole moment that enhances its solubility in water.

REFERENCES

https://pubchem.ncbi.nlm.nih.gov/compound/Hydrochloric-acid#section=2D-Structure

See also:

• Hydrogen Chloride Molecular Weight Calculation
• Hydrochloric Acid
• Hydrogen Chloride (HCl)
• Molarity of 37% (w/w) Hydrochloric Acid (HCl)
• How to Calculate Molarity of 37% (w/w) Hydrochloric acid (HCl), Alternative Method