Molarity of 70% (w/w) Nitric acid (HNO3)

Molarity of 70% (w/w) Nitric acid (HNO3)

Overview:

  • Nitric acid is a clear colourless liquid. A 70% (w/w) concentrated Nitric acid can be obtained from different suppliers.
  • 70% (w/w) Nitric acid means that 100 grams of Nitric acid contains 70 grams of HNO3.
  • The density of 70% (w/w)Nitric acid is 1.413 g/ml at 25°C that means that weight of the 1 ml of Nitric acid is 1.413 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 HNO3 is equal to 63.01 grams of HNO3 (molecular weight = 63.01).

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Calculation procedure:

Known values:
Density of Nitric acid :                                1.413 g/ml
Molecular weight of HNO3:                       63.01 g/mole

Concentration of Nitric acid:                     70% (% by mass, wt/wt)

Step 1: Calculate the volume of 100 grams of Nitric acid.

Formula:
Density =  weight / volume    or

Volume =  weight / density    or

Volume of 100 gram of Nitric acid : 100/1.413 =  70.771 ml

Note: 70% (w/w) Nitric acid means that 100 grams of Nitric acid contain 70 grams of HNO3.

The volume of 100 grams of Nitric acid is 70.771 ml. That means 70 grams of HNO3 is present in 70.771 ml of Nitric acid.

Step 2: Calculate how many grams of HNO3 is present in 1000 ml of Nitric acid.

70.771 ml of Nitric acid contain        = 70 grams of HNO3
1 ml of Nitric acid will contain           = 70/70.771 grams of HNO3

1000 ml of Nitric acid will contain    = 1000 x 70/70.771 = 989.106 grams of HNO3

1000 ml of Nitric acid will contain 989.106 grams of HNO3

Step 3: Calculate number of moles of HNO3 present in 989,106 grams of HNO3.

63.01 grams of HNO3 is equal to 1 mole.
1 gram of HNO3 will be equal to 1/63.01 moles.

989.106 grams will be equal to = 989.106 x 1/63.01 = 15.6976 moles

Therefore, we can say that 1 litre of Nitric acid contains 15.6976 moles or in other words molarity of 70% (w/w) Nitric acid is equal to 15.6976 M.