Dhristi JEE 2022-24

Introduction to Weak Electrolytes

A substance produces an electrically conducting solution when it is dissolved in polar solvents such as water. These types of substances are called electrolytes. The dissolved substance can be separated in the form of cations and anions that are dispersed in the solvent uniformly. This solution is in the neutral condition, electrically. 

 

When we apply electric potential to such types of solutions, the cations present in the solution get attracted to or drawn towards the electrode that has an abundance of electrons, and in the case of anions, these are directed or attracted towards the electrode that lacks or is deficient in electrons. This opposite movement of the cations and anions results in the production of electric current. Some examples of electrolytes are soluble salts, bases, and acids. In some conditions, gases such as HCl or hydrogen chloride can also act as electrolytes; such conditions include low pressure or high temperature. 

 

Types of Electrolytes

Polyelectrolytes are formed with the help of the dissolution of some of the synthetic polymers and biological polymers that contain charged functional groups. A substance has the capability to conduct electricity when it is dissociated into ions in the solution. The classification of strong and weak electrolytes is given below. 

 

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There are two types of electrolytes:

  1. Strong Electrolytes: If an electrolyte is completely dissociated into the solution, then such types of electrolytes are known as Strong electrolytes.

  2. Weak Electrolytes: If an electrolyte is not completely dissociated into the solution, then such types of electrolytes are known as weak electrolytes.

 

In the case of weak electrolytes, only a small fraction of the ions are present in a dissolved solute. Let us learn more about them.

 

What Are Strong Electrolytes and Weak Electrolytes?

The solid crystalline salts start dissociating into the paired charged particles when dissolved in a solvent. This was observed by a scientist named Svante Arrhenius in the year 1884. For this invention, he received the Nobel Prize in the year 1903. The salts that dissociate in the solvent as charged particles were named by Micheal Faraday as “ions”. According to Faraday, ions are produced by the process of electrolysis. But Arrhenius found that even in the absence of an electric current, salts contain ions and hence chemical reactions occur as a result of reactions in between the ions.

 

Weak electrolytes do not completely dissociate into the solvent, whereas strong electrolytes can dissolve in the aqueous solution. The solution contains both molecules and the ions that are present in the electrolyte. Weak electrolytes ionise partially in water but strong electrolytes ionise completely. Weak bases and weak acids are considered weak electrolytes. Strong bases, strong acids, and salts are considered strong electrolytes. Salt is considered a strong electrolyte even though it has low solubility in the water because whatever the amount it dissolves in the water is completely ionised. 

Weak electrolyte examples: Acetic acid (CH3COOH): Acetic acid is the acid that is found in vinegar. It is an electrolyte that is extremely soluble in the water. But when it is dissolved in the water, most of its original molecule remains as it is, instead of being in the ion form. This original form is known as ethanoate. The acetic acid is dissolved in the water and ionises as ethanoate and the hydronium ion. Thus, this makes acetic acid a weak electrolyte.

 

 CH3COOH + H2O ⇔ CH3COO -+ H3O +

 

Carbonic acid (CH2O3), Ammonia (NH3), and Phosphoric acid (H3PO4) act as weak electrolytes.

 

Strong electrolytes examples: Hydrochloric acid (HCl), Sulfuric acid (H2SO4), sodium hydroxide (NaOH), and potassium hydroxide (KOH).

 

Difference Between Strong Electrolyte and Weak Electrolyte

Weak Electrolyte

Strong Electrolyte

These electrolytes are not dissolved completely in the solution.

These electrolytes are dissolved completely in the solution.

The ionisation is less.

The ionisation is more. 

Low electrical conductivity.

High electrical conductivity.

Ostwald’s dilution law is applicable.

Ostwald’s dilution law cannot be applicable. 

Since it is ionised partially in the molten state or solution it contains ions and undissociated molecules. 

Since it is ionised completely in the molten state or solution it contains ions in the molten state or solution.

Example: Hydrogen cyanide (HCN)

Example: Nitric acid (HNO3)

 

Importance

The physiological importance and rehydration of weak electrolytes are as follows:

  1. Physiological Importance: 

  • The primary ions that are present in the electrolyte are sodium (Na+), chloride (Cl-), magnesium(Mg 2+), hydrogen carbonate (HCO3- ), hydrogen phosphate (HPO42- ), calcium(Ca2+), and potassium (K+). These electric charge symbols represent that the substance is of ionic nature and has an imbalanced distribution of electrons. Sodium and potassium are required to maintain fluid balance and blood pressure control.

  • The complex and subtle electrolyte balance between the intracellular and extracellular environment is required for all multicellular organisms. That is in particular maintaining the precise osmotic gradient of the electrolyte is important. These types of gradients regulate the hydration of the body and maintain the pH of the blood, nerve and muscle functions. 

  • The electrolyte activity between the intracellular fluid and extracellular fluid or interstitial fluid is required to maintain the activity of the muscles and neurons. The specialised protein structures that are present in the plasma membrane of the cell are known as ion channels. Through these channels, the electrolytes enter and leave the cell.

 

  1. Rehydration: 

The electrolyte drinks that contain potassium and sodium salts are used in oral rehydration therapy. These salts help to replenish the concentration of electrolytes in the body that are dehydrated due to excessive consumption of alcohol, exercise, vomiting, starvation, or heavy sweating. Athletes who are found exercising in extreme conditions for more than two hours continuously have the risk of dehydration. Thus the oral consumption of electrolytes is required. The electrolyte drink can be prepared at home by using sugar, salt, and water in definite proportions. 

 

Conclusion

Electrolytes are found commonly in fruit juices, milk, nuts, vegetables and many fruits. It is found in two forms: strong and weak electrolytes. These can be strong bases and acids or weak bases and acids. Electrolytes can be measured by performing diagnostic procedures, where blood is tested with the ion-selective electrodes. The most often measured electrolytes are potassium and sodium.


FAQs on Weak Electrolytes

1. What is a weak electrolyte? Mention a few examples.

Weak electrolyte definition is as follows, the electrolyte that is not completely dissociated into the solution. Since the electrolyte is dissolved partially in the solvent, only a small fraction of the ions are present in a dissolved solute in the case of the weak electrolyte.


Weak Electrolyte Examples: Ammonia (NH3), Carbonic acid (CH2O3), Hydrofluoric acid (HF), Pyridine (C5H5N), Hydrogen cyanide (HCN), etc.

2. What is a strong electrolyte? Mention a few examples.

The electrolyte that has the capability to dissociate completely into the solution, such types of electrolytes are known as strong electrolytes. Since the electrolyte is dissolved completely in the solvent, a large fraction of the ions is present in a dissolved solute in the case of the strong electrolyte.


Examples of strong electrolytes include Lithium hydroxide (LiOH), Barium hydroxide Ba (OH)2, Carbonic acid (CH2O3), Nitric acid (HNO3), Sulfuric acid (H2SO4), etc.

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