# Overview:

• Hydrochloric acid is a clear colourless aqueous solution of hydrogen chloride (HCl) that can be supplied as a 37% (w/w) hydrogen chloride solution (see suppliers).
• 37% (w/w) hydrochloric acid means that 100 grams of hydrochloric acid contains 37 grams of hydrogen chloride.
• The density of 37% (w/w) hydrochloric acid is 1.2 g/ml at 25°C that means that weight of the 1 ml of hydrochloric acid is 1.2 gram at 25°C.
• Molarity refers to number of moles of the solute present in 1 litre of solution.
• In simple words, 1 mole is equal to atomic weight of the substance. For example, 1 mole of hydrogen chloride is equal to 36.46 grams of hydrogen chloride (molecular weight = 36.46).

# Calculation procedure:

Known values:
Density of Hydrochloric acid :                                1.2 g/ml
Molecular weight of Hydrogen chloride:             36.46 g/mole

Concentration of Hydrochloric acid:                     37% (% by mass, wt/wt)

## Step 1: Calculate the volume of 100 grams of Hydrochloric acid.

Formula:
Density =  weight / volume    or

Volume =  weight / density

Volume of 100 gram of Hydrochloric acid   =   100/1.2   =   83.33 ml

Note: 37% (w/w) Hydrochloric acid means that 100 grams of Hydrochloric acid contains 37 grams of Hydrogen chloride.

The volume of 100 grams of Hydrochloric acid is 83.33 ml. That means 37 grams of Hydrogen chloride is present in 83.33 ml of Hydrochloric acid.

## Step 2: Calculate how many grams of Hydrogen chloride is present in 1000 ml of Hydrochloric acid.

83.33 ml of Hydrochloric acid contains       =  37 grams of Hydrogen chloride.
1 ml of Hydrochloric acid will contain          =  37/83.33 grams of Hydrogen chloride.

1000 ml of Hydrochloric acid will contain    =  1000 x 37/83.33   =    444.01776 grams of acetic acid

1000 ml of Hydrochloric acid will contain 444.01776 grams of Hydrogen chloride.

## Step 3: Calculate the number of moles of Hydrogen chloride present in 444.01776 grams of Hydrogen chloride.

36.46 grams of Hydrogen chloride            =     1 mole
1 gram of Hydrogen chloride                     =     1/36.46 moles

444.01776 grams of Hydrogen chloride   =     444.01776 x 1/36.46    =   12.178 moles

Therefore, we can say that 1 liter of Hydrochloric acid contains 12.178 moles or in other words molarity of 37% (w/w) Hydrochloric acid is equal to 12.178.