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Potassium Reacting With Water

May 22, 2013

Introduction to reaction of potassium with water:

Potassium, K, on reaction with water produces potassium hydroxide and water. It also releases good amount of heat in the reaction. The reaction is more violent as compared with lithium or sodium, and releases a lot of heat in such a manner that the evolved hydrogen gas ignites.

2K + 2(H2O) `->` 2KOH + H2

The heat released in the reaction is good enough to initiate a hydrogen-oxygen reaction, which is considered explosive.

Potassium metal with water:

Potassium metals react vigorously or even explosively with cold water. In this case, a solution of the metal hydroxide is produced together with hydrogen gas. The metal hydroxide produces is known as potassium hydroxide.

2 K + 2H2O   `->`      2KOH +   H2

For this vigorously potassium with water reaction, reaction metal must be taken in large sealed containers. Potassium with water reaction occurs because potassium has high affinity towards water that provides a large amount of energy. This released energy over comes the activation energy of reaction of potassium with water.

Reaction details of potassium with water:

In the reaction of potassium with water, potassium disintegrates due to oxide and hydrogen corrosion, when exposed to air. To prevent this the most method followed is to store them under a hydrocarbon medium, which does not react with alkali metals, such as mineral oil or kerosene.

Potassium reacts rapidly with even traces of water, and its reaction products are nonvolatile, it is sometimes used alone, or as NaK (an alloy with sodium which is liquid at room temperature) to dry solvents.

Potassium hydroxide is a strong alkali, which causes skin burns. Finely divided potassium will ignite in air at room temperature. The bulk metal will ignite in air if heated. Water makes a potassium fire worse. Because its density is 0.89, burning potassium floats which exposes it to more oxygen that is atmospheric.

Potassium is contained in water of sea (around 400 parts per million) and it tries to settle, and sediment mostly. On the other hand, river water contains about 2-3 ppm potassium, due to basalts present in sea. In water, this element is mainly present as K+ (aq) ions.40K is a naturally abundant radioactive potassium isotope. Seawater contains a natural concentration of about 4.5 10-5 g/L.

reaction of potassium with water

reaction of potassium with water

Fig: – reaction of potassium with water

Potassium with water chemistry:

Potassium metal also floats on the surface of water, because it has less density than water when it come in contact in water in potassium with water reaction, but enough heat is given off to melt the potassium and it melts almost at once to form a small silvery globule ball that dashes around the surface. A white trail of pottsium hydroxide is seen in the water under the potassium, but this soon dissolves to give a colorless solution of potassium hydroxide.

The potassium moves because it is pushed around by the hydrogen which is given off during the reaction. If the potassium becomes trapped on the side of the container, the hydrogen may be get fire to burn with an orange flame. The color is due to contamination of the normally lilac (a faintly bluish pink) hydrogen flame with potassium compounds. Potassium with water reaction is much faster and it produces enough heat to light the hydrogen gas thus produces. Due to the potassium with water reaction it must be stored in kerosene oil.

Conclusion for reaction of potassium with water

As per the conclusion, we see that, potassium is not soluble in water but react with water as was explained earlier. Potassium compounds may be water-soluble. Potassium dichromate is soluble with a water solubility of 115 g/L.


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