What do bananas, oranges, potatoes, peas, mushrooms and cucumbers have in common? Yes, it is potassium. All these fruits are rich in potassium which helps us obtain essential nutrients upon consuming them. Potassium is the first element in the fourth row of the periodic table.
Potassium is derived from a material known as potash. There are proven facts that this element has been in existence for over hundreds and hundreds of years.
In this article, we will be discussing the physical and chemical properties of potassium in detail while also looking at other related concepts. It will motivate the aspirants of NEET 2022 to study well and help obtain the best possible marks in the examination.
Facts about potassium
The following are some of the facts about potassium that every Chemistry enthusiast should know:
- The atomic mass of potassium is 39.098, written in atomic mass units. Potassium is represented using the letter K.
- Potassium is an alkali metal, the same as francium, caesium, sodium, rubidium and lithium.
- Potassium was founded a long time ago, some hundreds of years ago.
- The name potassium comes from the name of a material called potash.
- Potassium is an active metal and could never be found separately in nature. It mostly forms compounds with other elements.
Sources of potassium
Potassium comes from a wide variety of sources in terms of food. The following are some of them:
- Whole grains
- Beans and nuts
- Lean meats
- Vegetables, especially carrots, potatoes, leafy greens
- Fruits, mainly kiwi, bananas, pineapples, oranges, apricots, etc.
While eating a balanced diet, it is possible to obtain essential nutrients with potassium intake. However, a doctor would prescribe the mineral one needs to take if they have low potassium levels.
While preparing for the NEET exam, the students often come across isotopes. Similarly, potassium is usually divided into three isotopes, namely potassium-39, potassium-40 and potassium-41.
Potassium-40 is commonly found in plants, rocks and animals and is described as a radioactive isotope. The main usage of this whole isotope concept is to figure out how old an element is.
While preparing for NEET 2022, the aspirants should also understand how this element occurs. It isn’t easy to procure potassium since it is majorly contained in shale, igneous rocks, and sediment in minerals such as orthoclase feldspar and muscovite. All these minerals are insoluble in water, so it makes it tougher.
Hence, soluble potassium compounds, namely langbeinite (K2 Mg2 SO43), polyhalite (K2 Ca2 Mg SO44 2 H2 O), sylvite (KCl) and carnallite (K Mg Cl3 6 H2 O) that are found in ancient sea beds and lake beds are electrolysed so that they could obtain commercial potassium compounds.
In addition to that, there is another way to produce potassium. It includes sodium reduction of molten KCl, which is nothing but potassium chloride, at 870 ℃. The process can be done by feeding the molten potassium chloride into a packed distillation column. Here, the vapour of sodium is allowed to pass through the column. Therefore, if the potassium contains higher volatility, it will end up at the top of the distillation tower.
Physical and chemical properties of potassium
Potassium possesses many chemical and physical properties that the NEET aspirants should know before appearing for their examination. Some of the major ones are listed below:
- Potassium is seen as a silky, lustrous metal with a boiling point of 770 ℉ and a melting point of 63 ℉.
- The metal potassium is capable of floating in the water.
- Its reaction could be aggressive with water, which will produce hydrogen. The creation could have the possibility of catching fire followed by an explosion.
- Elements easily reacted with potassium include fluorine, chlorine, phosphorus, nitrogen and sulphur.
- Potassium consists of a flame lavender in colour and could generate green smoke.
- Potassium is the seventh most earth element which is found in the crust.
- Tracing potassium is always accomplished with the help of other elements.
- It is a malleable metal and is covered in a silver colour profile once isolated.
- Potassium contributes upto 2.6 % of the earth’s mass.
- Its atomic number is 19, and its atomic weight is 39.08 u.
- The specific gravity of potassium is 0.862 at 20 ℃.
- There are two oxidation states for potassium. They are +1 and -1. In that, -1 is only rarely used.
- The electronegativity marking for potassium is 0.82, according to Pauling.
- Potassium has a density of 0.86 g cm3 at 0 ℃.
- The measurement of its Van der Waals radius comes around 0.235 nm.
- The ionic radius of potassium is 0.133 nm.
- The first isolation energy of potassium is 418.6 KJ mol-1.
Chemical reactions involving potassium
Another fundamental thing about potassium that every NEET Chemistry aspirant should know is how it reacts with other chemical substances. Let us see some of them in detail:
- Potassium’s reaction with water:
The reaction of potassium in water is rigorous and rapid. The result is the formation of a colourless solution that includes hydrogen gas and potassium hydroxide. The reaction involved is exothermic, and the nature of the product is basic. The rate of this reaction is faster than the rate of the reaction of sodium with water but slower than rubidium.
2 K s+2 H2 O →2 K O H aq+H2 (g)
- Potassium’s reaction with air:
Although potassium looks shiny while cutting it, the reaction with moisture and air contained in it tarnishes it. While burning potassium in the air, potassium superoxide (K O2) is formed. Its colour is red.
K s+O2 g →K O2 (s)
- Potassium’s reaction with acids:
Usually, potassium can dissolve in a solution of dilute sulphuric acid, which could form solutions consisting of aquated K (I) ions together with hydrogen gas.
2 K s+H2 SO4 aq →2 K+ aq+S O42- aq+H2 (g)
- Potassium’s reaction with oxygen:
Potassium oxide is seen as an ionic compound consisting of oxygen and potassium. Because it is highly reactive, it will turn into a mixture of potassium superoxide and potassium peroxide. Treating the potassium peroxide will yield potassium oxide.
K2 O2+2 K →2 K2 O
- Potassium’s reaction with halogens:
In Chemistry, when there is a reaction between potassium and halogens, there will be a formation of potassium halides. Given-below is the reaction for the same, which is a little bit complex:
- Potassium fluoride:
2 K s+F2 g →K F (s)
- Potassium iodide:
2 K s+I2 g →K I (s)
- Potassium bromide:
2 K s+Br2 g →K Br (s)
- Potassium chloride:
2 K s+Cl2 g →K Cl (s)
Applications of potassium
Potassium has numerous applications and uses. The NEET Chemistry aspirants should be aware of the following applications:
- The most amount of potassium is used in making fertilisers. An estimated amount of 95 % of potassium has been utilised for that purpose. Meanwhile, the rest goes into making potassium hydroxide (KOH). The entire thing is done with the assistance of an electrolyte solution of potassium chloride, followed by converting it to potassium carbonate (K2 CO3).
- Potassium carbonate is used in manufacturing glasses. These glasses are mainly used to make televisions.
- Potassium hydroxide can be utilised to make liquid detergents and soaps.
- Potassium chloride is mainly used in pharmaceuticals, especially in saline injections and medical drips.
- Other potassium salts can be utilised in tanning leather, baking, salt iodisation, etc.
The key to their usage in all the cases mentioned above is the negative anion and not the potassium itself.
A NEET aspirant should know the possible causes of potassium deficiency in their bodies. There is another term called hypokalemia that occurs due to potassium deficiency. It includes:
- Overuse of diuretics
- Kidney disease
- Magnesium deficiency
- Diarrhoea, excessive sweating and vomiting
- The utilisation of antibiotics, namely penicillin and carbenicillin
Hypokalemia symptoms can vary depending on the severity of the deficiency. A temporary reduction in potassium might not cause any symptoms. For instance, sweating (after burning the calories after a workout) will not have any immediate impact. The person takes a meal and normalises their eating before it causes any serious damage.
Overdose of potassium is capable of causing a disease called hyperkalemia. However, it is somewhat rare in people who take balanced diets. The following are a few risk factors for an overdose of potassium:
- Prolonged exercise
- Kidney disease
- Taking too many supplements of potassium
- Potassium-conserving diuretics
- Severe burns
In conclusion, the students of NEET 2022 Chemistry are taught about potassium in general, which includes understanding some of the facts while briefly discussing the various sources of potassium. Moreover, we have also discussed the potassium isotopes and occurrences of potassium in detail.
In addition to that, the students gained complete knowledge of potassium’s chemical and physical properties. Furthermore, detailed information on different chemical reactions on potassium is also given. Later on, the aspirants understand where this element is utilised. Finally, the causes of potassium deficiency and overdose have also been discussed.