[Chemistry Class Notes] on Potassium Pdf for Exam

Potassium is the first element in the periodic table’s fourth period (row).

• Potassium has an atomic mass of 39.098 atomic mass units. It’s represented by the letter ‘K.’

• Potassium comes from a material called Potash.

• For hundreds of years, the element has been employed.

• It is an alkali metal, like lithium, rubidium, sodium, caesium, and francium.

• It is an extremely active metal that is never found alone in nature; instead, it forms compounds with other elements.

Potassium’s Applications

• Because of this, it may be used as a heat exchange medium and is employed in nuclear power plants.

• Potassium salts are used as a fertilizer component.

• It is one of the human body’s basic nutrients.

• Injections with potassium chloride are also common.

• Potash can be used to create glass, soap, and other products.

Metal Potassium

Potassium (K) is a chemical element in the alkali metal group of the periodic table, belonging to Group 1 (IA). It is necessary for both plant and animal life to exist.

Potassium Isotopes

Potassium is commonly divided into three isotopes: potassium-39, 40, and 41. Potassium-40 is a radioactive isotope that can be found in rocks, plants, and animals. It’s used to figure out how old something is. This isotope degrades into an argon isotope.

Potassium’s Physical and Chemical Properties

• It is a silky, lustrous metal with a melting point of 63°F and a boiling point of 770°F.

• The metal potassium can float in water.

• It reacts aggressively with water, producing hydrogen, which can catch fire and explode.

• Chlorine, fluorine, sulphur, nitrogen, and phosphorus are all easy to react with.

• It has a lavender-coloured flame and green smoke.

• It is the seventh most prevalent element in the crust of the world.

• When tracing the element, it is always done in conjunction with other components.

• Potassium is a malleable metal with a silver colour profile once isolated.

• Potassium interacts aggressively with water, releasing hydrogen gas.

Potassium-Related Information

• The phrase Kalium is represented by the symbol K.

• It comes from the phrase “alkali,” which is an ancient designation for the element.

• Potassium, like the other elements in the first column, is an alkali group member, along with caesium and sodium.

• It was the first metal to be electrolyzed and isolated.

Potassium is an alkali metal and is a part of group 1. Its symbol is K taken from its Latin name Kalium. Its atomic number is 19 and atomic weight is 39.098u. It is white with a silvery shine or luster. It is soft at room temperature. It has a low melting point (63.28 °C or 145.90 °F). Its boiling point is (760 °C or 1,400 °F). Potassium is a fine conductor of electricity and heat. 

 

 

Its electronic configuration is 2, 8, 8, 1 or we can say 1s2 2s2 2p6 3s2 3p6 4s1.

 

History

Potassium was first isolated from caustic potash KOH (molten) by electrolysis in 1807. It was done by Sir Humphry Davy. Potassium collected at the cathode. 

 

A notable point is that the very first metal to be isolated by electrolysis is Potassium. Until then, Potassium and Sodium could not be distinguished from each other. Before potassium was recognized as an element, it was used to make soap by mixing potassium carbonate with animal fat.

Physical Properties

Potassium is the seventh most abundant element found on Earth’s crust. It constitutes 2.6 percent of Earth’s mass. The element whose atomic number is 19 and atomic weight 39.098u has a melting point of 63.28°C and a boiling point of 760°C. Its specific gravity is 0.862 at 20°C. Potassium has two oxidation states +1 and -1(rarely).

There are three isotopes for potassium which are naturally present: potassium-39, potassium-41, radioactive potassium-40. Several artificial isotopes have also been prepared. 

Occurrence 

Since potassium is mainly present in igneous rocks, shale, and sediment in minerals like muscovite and orthoclase feldspar, it is difficult to procure the element itself. The fact that these minerals are insoluble in water makes the job tougher. Therefore, soluble potassium compounds such as carnallite (KMgCl3.6H2O), sylvite (KCl), polyhalite (K2Ca2Mg [SO4]4.2H2O), and langbeinite (K2Mg2 [SO4]3) which are found in ancient lake beds and sea beds are electrolyzed to obtain commercial compounds of potassium.

Another way to produce potassium is to do sodium reduction of molten potassium chloride, KCl, at 870°C. This is done by feeding molten KCl into a packed distillation column. Sodium vapor is passed up through the column alongside. More volatile potassium will be condensed at the top of the distillation tower. 

Chemical Properties

The element whose atomic number is 19 has 0.82 marking for electronegativity (according to Pauling). It has a density of 0.86 g.cm-3 at 0°C. It’s Van der Waals radius measures to 0.235 nm. It has an ionic radius of 0.133 nm. The energy of the first isolation is 418.6 kJ.mol-1.

Reactions Involving Potassium

Though potassium is shiny when it’s cut, the reaction with air and moisture present in it tarnishes it. When potassium is burned in air, potassium superoxide (KO2) is formed. It is orange in color.

K(s) + O2(g) → KO2(s)

Potassium reacts rapidly and vigorously with water to form potassium hydroxide and hydrogen gas in the form of a colorless solution. The product is basic in nature. The reaction is exothermic.

2K(s) + 2H2O → 2KOH (aq) + H2 (g)

The reaction is fast, higher than the rate of sodium reacting with water but lower than rubidium.

Formation of potassium halides occurs when potassium reacts with halogens. The reaction is quite vigorous.

2K(s) + F2 (g) → KF(s) potassium fluoride

2K(s) + Cl2 (g) → KCl(s) potassium chloride

2K(s) + Br2 (g) → KBr(s) potassium bromide

2K(s) + I2 (g) → KI(s) potassium iodide

Potassium dissolves readily in dilute sulphuric acid to form solutions containing the aquated K (I) ion together with hydrogen gas.

2K(s) + H2SO4 (aq) → 2K+ (aq) + SO42-(aq) + H2 (g)

• Potassium oxide is an ionic compound of potassium and oxygen. Since it is highly reactive, it turns into a mixture of potassium peroxide and potassium superoxide. Treatment of potassium peroxide yields potassium oxide.

 

 

K2O2 + 2 K → 2 K2O

Uses

Since potassium forms a lot of compounds, it is a very useful element. Potassium chloride (KCl) can be called as the most common potassium compound. It is used in fertilizers and also as a salt substitute. It can be used to produce other chemicals as well. Potassium hydroxide (KOH) is used in the manufacture of soaps, detergents and drain cleaners. Potassium carbonate (KHCO3) is used to make certain types of glass and soaps. It is obtained as a byproduct of the commercial production of ammonia. KHCO3 is also known as pearl ash. Potassium nitrate (KNO₃) is used in the production of fertilizers, match heads and also pyrotechnics.