Potassium Nitrate Molar Mass, Formula and Uses

Potassium nitrate (KNO3), its common name is saltpeter, is a chemical compound consisting of potassium, nitrogen, and oxygen and is a crystalline salt that is soluble in water and has a color ranging from white to colorless.

Potassium Nitrate Molar Mass

Potassium (K): 39.10 g/mol

Nitrogen (N): 14.01 g/mol

Oxygen (O): 16.00 g/mol (there are three oxygen atoms in KNO3)

Molar mass of KNO3 = 39.10 + 14.01 + 16.00x 3

= 39.10 + 14.01 + 48.00 

= 101.11 g/mol

Therefore, the molar mass of potassium nitrate is 101.11 g/mol.

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Potassium Nitrate Chemical Formula

The chemical formula for potassium nitrate is KNO3. Its molecular structure consists of one potassium (K) atom, one nitrogen (N) atom, and three oxygen (O) atoms. The K atom is bound to one of the O atoms, while the N atom is bound to the other two O atoms. 

Potassium Nitrate Molar Mass, Formula and Uses

The three O atoms are arranged around the N atom in a trigonal planar geometry. The chemical bonds in potassium nitrate are ionic, in which the K atom donates an electron to each of the three O atoms to form the KNO3 molecule.

Potassium Nitrate Uses

1. Potassium nitrate is used in fertilizers as a source of nitrogen and potassium. This is especially useful for crops that require high levels of potassium.

2. It is used as a preservative in some types of meat products, such as bacon, ham, and hot dogs. 

3. It is used as an oxidizer in fireworks and other pyrotechnic devices. 

4. It is a major component in gunpowder, which is used as a propellant for firearms and other weapons.

5. This can be used to accelerate the decomposition of tree stumps, making them easier to remove.

6. It is used in some medicines to treat certain medical conditions like high blood pressure and angina.

How to Make Potassium Nitrate?

Potassium nitrate (KNO3) is synthesized using several different methods, but a common method is by reacting potassium chloride (KCl) with sodium nitrate (NaNO3) in the presence of a strong acid.

2KCl + NaNO3 + H2SO4 → 2HCl + KNO3 + NaHSO4

This reaction produces potassium nitrate (KNO3) as well as hydrochloric acid (HCl) and sodium bisulfate (NaHSO4) as byproducts. This reaction is completed in the following steps.

Materials Needed to

  • Potassium chloride (KCl)
  • Sodium nitrate (NaNO3)
  • Concentrated sulfuric acid (H2SO4)
  • Distilled water
  • Heat source
  • Glassware and laboratory equipment (beakers, flasks, stirring rod, thermometer, etc.)


Take 90 grams of potassium chloride (KCl) and 110 grams of sodium nitrate (NaNO3) in a clean and dry beaker. Mix the two solids thoroughly using a stirring rod.

In take a separate beaker, add 160 milliliters of concentrated sulfuric acid (H2SO4) to 80 milliliters of distilled water. Stir the mixture until it is a homogeneous mixture.

With constant stirring, gradually add the acid mixture to the solid mixture. The reaction will produce a lot of heat and gas, so be careful to add the acid mixture slowly and not stir as much.

Heat the reaction mixture using a heat source (such as a hot plate or Bunsen burner) to maintain a temperature of 200-250 °C. And keep stirring the mixture.

This reaction begins to produce hydrochloric acid (HCl) gas, which must be removed from the reaction vessel using a fume hood or other ventilation system. The reaction mixture will also begin to turn yellow and emit brown fumes.

After heating for about 30 minutes, the reaction is complete and the brown fumes stop. Now let the mixture cool down to room temperature.

Pour the cooled mixture into a large beaker and add about 500 ml of distilled water to it. The mixture is stirred well to dissolve the potassium nitrate (KNO3).

The mixture is filtered through filter paper to remove the impurities or undissolved solids present in it.

The filtrate contains potassium nitrate (KNO3) dissolved in water. To obtain solid potassium nitrate, the water is evaporated using a heat source until crystals begin to form. The mixture is allowed to cool and then the crystals are filtered to obtain pure potassium nitrate.

NOTE: This reaction contains concentrated sulfuric acid, which is highly corrosive and can cause severe burns. This should only be done by experienced chemists with proper safety equipment and procedures.


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