The molarity of 25% (w/w) Hydrochloric Acid is 7.68 M.

## OVERVIEW

A 25% (w/w) Hydrochloric Acid is a clear colorless aqueous solution of Hydrogen chloride (HCl) gas. It can be purchased from many Suppliers.

The “%” refers to solution concentration in percentage and “(w/w)” refers to solute and solution amount given in grams (i.e., percentage by weight). This means a 25% (w/w) Hydrochloric acid contains 25 g of HCl per 100 g of solution.

The density of 25% (w/w) Hydrochloric acid solution is 1.12 g/ml at 20°C which means the weight of the 1 ml of the hydrochloric acid solution is 1.12 g at 20°C.

Molarity refers to the number of moles of the solute present in 1 liter of solution. To calculate the Molarity of 25% (w/w) Hydrochloric acid (HCl), you need to know how many moles of HCl are present in 1 liter of solution. In simple words, 1 mole is equal to the molecular weight of the substance. For example, 1 mole of Hydrogen chloride is equal to 36.46 g of hydrogen chloride (Molecular Weight: 36.46). To calculate the molarity, one must first calculate how much Hydrogen chloride is present in 1 L of 25% Hydrochloric acid. Once we know the amount of HCl present in 1 L solution, we can calculate the molarity of the solution by dividing the HCl amount by the molecular weight.

**Calculation procedure: **Molarity of 25% (w/w) Hydrochloric acid (HCl)

Known values | |

Molar mass of Hydrogen chloride | 36.46 g/mole |

Concentration of Hydrochloric acid | 25% (% by mass, w/w) |

Density of 37% Hydrochloric acid | 1.12 g/ml |

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

Formula:

Density = Weight/Volume

OR

Volume = Weight/Density

The volume of 100 g of Hydrochloric acid: 100/1.12 = 89.2857 ml

Note: 25% (w/w) hydrochloric acid means 100 g of solution contains 25 g of HCl.

The volume of 100 g of Hydrochloric acid is 89.2857 ml which means 25 g of HCl is present in 89.2857 ml of Hydrochloric acid.

**Step 2: Calculate how many grams of HCl is present in 1000 ml of Hydrochloric acid.**

89.2857 ml of Hydrochloric acid contains = 25 grams of HCl

1 ml of Hydrochloric acid will contain = 25/89.2857 grams of HCl

1000 ml of Hydrochloric acid will contain = (1000 x 25)/89.2857 = 280.00 grams of HCl

1000 ml of Hydrochloric acid will contain 280.00 grams of HCl.

**Step 3: Calculate the number of moles of HCl in 280.00 grams of HCl.**

36.46 g of HCl is equal to 1 mole.

1 g of HCl will be equal to 1/36.46 moles.

280.00 grams of Hydrogen chloride will be equal to = (280.00 x 1)/36.46 = 7.68 moles

Therefore, we can say that 1 liter of Hydrochloric acid contains 7.68 moles of HCl or in other words molarity of 25% (w/w) Hydrochloric acid is equal to 7.68 M.

## Molarity of 25% (w/w) Hydrochloric acid (HCl)

**Calculator – Calculate the molarity of concentrated Hydrochloric acid (HCl)**

**Hydrogen Chloride (HCl) Molecular weight:** 36.46 g/mole

**Concentration of Hydrochloric acid:**% (wt/wt)

(Change the % (wt/wt) concentration)

**Density of glacial Hydrochloric acid:** g/ml

(Change the density)

**Molarity of Hydrochloric acid:** 7.68 M

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