The molecular weight of Hydrogen chloride (HCl) is 36.4607.

Hydrogen chloride (HCl) is an inorganic compound of two elements: Hydrogen and Chlorine. The molecular weight of Hydrogen chloride is 36.458 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of all its elements.

CALCULATION PROCEDURE

Step 1: Find out the chemical formula and determine constituent atoms and their number in a hydrogen chloride molecule. 
You will know different atoms and their number in a hydrogen chloride molecule from the chemical formula. The chemical formula of hydrogen chloride is HCl. From the chemical formula, you can find that one molecule of Hydrogen chloride consists of one Hydrogen (H) atom, and one Chlorine atom.

Step 2: Find out atomic weights of each atom (from the periodic table). 

Atomic weight of Hydrogen (H): 1.008 (Ref: Lanl-1)
Atomic weight of Chlorine (Cl): 35.4527 (Ref: jlab-ele017)

Step 3: Calculate the total weight of each atom present in hydrogen chloride by multiplying its number by its atomic weight. 

Number of hydrogen atoms in hydrogen chloride: 1
Atomic weight of hydrogen: 1.008
Total weight of hydrogen atoms in hydrogen chloride: 1 x 1.008 = 1.008

Number of chlorine atoms in hydrogen chloride: 1
Atomic weight of chlorine: 35.4527
Total weight of chlorine atoms in hydrogen chloride: 1 x 35.4527 = 35.4527

Step 4: Calculate the molecular weight of hydrogen chloride by adding the total weight of all atoms. 

Molecular weight of hydrogen chloride (HCl): 

1.008 (1.008 x 1 hydrogen) + 35.4527 (35.4527 x 1 chlorine)

So the molecular weight of hydrogen chloride is 36.4607.

REFERENCES:

• Pubchem-Hydrogen : https://pubchem.ncbi.nlm.nih.gov/element/Hydrogen 
• Lanl-1: https://periodic.lanl.gov/1.shtml 
• jlab-ele017: https://education.jlab.org/itselemental/ele017.html
• Pubchem-Chlorine: https://pubchem.ncbi.nlm.nih.gov/element/Chlorine

See also:

• Hydrogen chloride molecular weight calculation
• Hydrochloric Acid
• Hydrogen Chloride (HCl)
• Molarity of 37% (w/w) hydrochloric acid (HCl)
• Molarity of 37% (w/w) hydrochloric acid (HCl), alternative method