Alkali and Alkaline Solution

Alkali is an ionic salt that produces hydroxide ions when dissolved in water. Alkali metals react vigorously with water and produce hydroxides. Alkalis are basic. Alkali can be defined as the basic water-soluble ionic salt having a pH value greater than 7. Here pH value greater than 7 indicates that Alkalis are basic. The word alkali is taken from the Arabic word 'qali'  which means ‘from the ashes’. Alkali salts are soluble hydroxide compounds of alkali metals and alkaline earth metals. Alkali examples are the salts of alkali and alkaline earth metals such as sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2) and magnesium hydroxide (Mg(OH)2)  etc. The alkaline properties of alkalis are due to the presence of hydroxide ions. 

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Properties of Alkali

Various alkali examples are seen in day to day life. Alkalis possess some chemical and physical properties. Some of the important properties of alkali are as follows:

• Their taste is bitter and has a soapy touch.

• Alkali turns red litmus paper to blue which shows a high concentration of hydroxide ions in the solution.

• They are conductors of electricity because of the presence of mobile ions.

• When alkalis are mixed with acid. They produce salt and water. This reaction is known as a neutralization reaction.

• Alkali can produce ammonia gas when they react with ammonium salts.

• Strong alkali solutions are corrosive. Some strong alkali solutions are highly corrosive.

• They are highly soluble in water.

• The indicators are used to determine the strength of Alkalis whether they are strong or weak base.

• The alkali and alkaline earth metals are soft and shiny and form ionic compounds.

Uses of Alkali

Alkalis have various uses in our daily life and industrial purposes. Some of the uses of Alkalis are given below:

• Sodium Hydroxide is an Alkali that is used in the manufacturing of papers, soaps and detergents.

• Calcium Hydroxide ( acidic slaked lime) is added to lakes to make them less acidic.

• Calcium Carbonate is used in construction works.

• Potassium Hydroxide is used for agricultural purposes to make acidic soil alkaline soil for better growing of plants.

• Stomach Indigestion is caused in our stomach due to excessive amounts of Hydrochloric Acid (HCl). The problem of indigestion can be cured by taking tablets containing bases such as magnesium hydroxide or calcium carbonate to neutralise the acid.

• The sting of the bee is acidic which can be cured by neutralizing it with an alkali such as ammonia solution.

• Alkali is used in various chemicals for industrial purposes.

What is Alkaline Solution?

Alkaline solutions are the solution of a solid base in water. When Alkalis are dissolved in water then the solution is known as Alkaline solution. The Alkaline solutions are basic in nature and have several industrial, laboratory and daily life applications. In simple words, an alkaline solution meaning is a solution that is made from alkalis. All alkaline solutions are basic in nature, but not all bases are alkaline. Sometimes alkaline solutions and bases are misinterpreted. Alkaline solutions and base are not the same. The alkaline solution is the solution of alkali in the water while the base that is not soluble in water then their solution will not be an alkaline solution. Some formulas of alkali salts are Mg(OH)2, NaOH, Ca(OH)2, Be(OH)2 and these salts when dissolved in water give the alkaline solution so these are alkaline formula in chemistry.

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Properties of Alkaline Solution

The properties of alkaline solutions are given below:

• The hydroxide of alkaline earth metals is less soluble than the alkali metal hydroxides.

• To determine the strength of the solution universal indicators are used such as litmus paper and phenolphthalein indicators. Alkaline solutions turn red litmus paper to blue and phenolphthalein from colourless to pink which shows the basic nature of an alkaline solution.

• The strong alkaline solution is a corrosive liquid.

• Their pH value is greater than 7.

• They are bitter in taste.

• Alkaline solutions are good conductors of electricity.

• They perform neutralization reactions when mixed with acid and produce salt and water.

Uses of Alkaline Solution

Alkaline Solutions have several uses due to their alkaline nature. There are some uses of alkaline solutions:

• The kitchen cleaners are made of alkaline solutions such as ammonia and sodium hypochlorite.

• Strong alkaline solutions are used as electrolytes in zinc-air batteries.

• Ammonia solutions are also used in manufacturing fertilizers.

• Strong alkaline solutions can damage skin, therefore weak alkaline solutions are used in daily life such as soap, toothpaste are cleaners.

• Chlorine bleach is an example of an alkaline solution. In chlorine bleach, sodium hypochlorite is dissolved in water. It is used to clean and whiten fabrics as well as surfaces, chlorine bleach also works as an effective disinfectant.

• Some vegetables and plants grow in alkaline soil. So alkaline solutions are added to the soil to make it slightly alkaline.

• Alkaline solutions are slippery or soapy to the touch, due to saponification so they are used in soaps and detergents.

Difference between Alkali and Alkaline

When a substance is dissolved in water, it makes a solution. The nature of the solution can be acidic, alkaline or neutral depending upon the property of the solution. When the solute is ionic, it gives ions in the solution. Hydroxide ions give basic properties to the solution while Hydrogen ions give acidic properties to the solution. If the solution is neutral that means the concentration of hydrogen ions and hydroxide ions are equal in the solution. When alkali metals are dissolved in water then they produce alkaline solutions. Alkali and alkaline terms are also related to the periodic table. There are two groups in the modern periodic table; group 1 and group 2 whose elements are called alkali metals and alkaline earth metals respectively. Both alkali and alkaline earth metals from an alkaline solution. The difference between alkali and alkaline earth metals are given below:

When a substance called solute is dissolved in another substance called solvent then the solution is formed. The nature of the solution can be acidic, basic or neutral because of the concentration of ions present in the solution. The alkaline base nature of the solution is due to the presence of hydroxide ions. This type of solution is called alkaline solution and if the alkaline nature of the solutions comes from the alkali solutes. 

Did You Know?

• The alkali metals of group 1 of the periodic table are the most active metals; they react with water to form hydrogen gas and hydroxide ions. The elements of group 1 are Lithium, Sodium, Potassium, Rubidium, Caesium and Francium.

• pH scales are used to measure the concentration of acidic and basic ions in the solutions. It ranges from 0 to 14 in order of decreasing acidity and increasing basicity.