What is Salt Bridge?

A salt leg is a device used in an electrochemical cell because that connecting that oxidation and also reduction fifty percent cells within a weak electrolyte is used. In other words, a salt leg is a junction that connects the anodic and cathodic compartments in a cell or electrolytic solution.

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The salt leg usually consists of a solid electrolyte i m sorry is further made up of ions. Because that example, AgNO3, KCl, etc. Salt bridges are usually used in a galvanic cell such together a voltaic cabinet or Daniel cell.

Salt bridge Function

The main role of a salt leg is to help maintain the electric neutrality in ~ the interior circuit. It likewise helps in preventing the cell from taking its reaction to equilibrium. If salt bridges are missing or if they space not offered then the reaction will most likely continue and also the solution in one-half electrodes will gather a negative charge. Similarly, in the other half, electrodes would certainly accumulate a confident charge. This will certainly further result in the stoppage that the reaction and also no electrical power will it is in produced.


Therefore, a salt bridge basically help in avoiding the build-up of confident and an adverse charges around the particular electrodes and further allowing a smooth reaction to take it place. It also helps in the continual flow the electrons. However, the objective of a salt bridge is not to relocate electrons indigenous the electrolyte; fairly it’s to preserve charge balance since the electron are relocating from one-half cell to the other.

Salt bridge avoids the diffusion or mechanical circulation of equipment from one-half cell to another.It avoids or minimizes the liquid-liquid junction potential. (Potential arises between two solutions once they space in call with each other).Salt bridge acts together an electric contact between two fifty percent cells.

Types of Salt Bridges

There are largely two varieties of salt bridges offered in electrochemical cells.

Glass pipe BridgeFilter file Bridge

Glass tube Bridge

They are usually U – shame Tubes filled with electrolyte. Sodium Chloride (NaCl), Potassium Chloride (KCl), Potassium Nitrate (KNO3) is usually used electrolyte. The electrolyte needs to be relatively unreactive with other chemicals in the cell and also have cations and anions with similar migratory rate (comparable ion charge and also molecular weight).

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The electrolytes are often held as gelatin such together Agar-Agar. The concentration of salt solution and also diameter of the glass pipe plays an important role in conductivity. Lowering the concentration and the diameter the the pipe decreases the conductivity.

Filter document Bridge

They are one more most typically used bridge, covers filter file or porous material soaked in electrolyte. Here, sodium chloride (NaCl) or potassium chloride (KCl) are typically used electrolyte. Electrolytic concentration, porosity, and also roughness of filter document affect the conductivity. For higher conductivity, a filter file with smooth absorbent is used, they yield greater conductivity than rough file with reduced absorbent.

As stated above, a salt bridge’s main role is to maintain the electric neutrality between two beakers. To do so the salt used have to be inert. The ions need to relocate to and forth between the two half cells. Unlike various other salts, potassium chloride (KCl) and also potassium nitrate (KNO3) are far better inert salts. An inert salt is used to protect against the reaction from occurring between the salt and solution. The inert salt potassium chloride (KCl) is a typically used salt due to the fact that the potassium and also chloride ions have very common diffusion coefficient and also minimizing junction potential, yet the potassium chloride is unwise to use as electrolyte as soon as the electrode supplied is command or silver because they form a precipitate.

Salt leg in Electrolysis

Like in the electrochemical cell, salt bridges have actually the same duty in electrolytic cell too. If we immerse the 2 electrodes in one systems in a solitary container, no salt leg is necessary, however if we desire each electrode in a various solution and also in different containers, we need a salt leg to complete the circuit. It consists of mobile ion that action as charge carriers.

Preparing Salt Bridge

Soaking String, Cotton, or document Material in an Electrolyte Solution

For preparing a bridge, take product that is huge enough to reach two beakers. Ar this product in a pool of electrolyte till they acquire saturated through the solution. Carefully take the product from the electrolytic solution and also remove the excess lot of electrolyte.

Preparing gel to duty as Bridge

The gelatin is rely in one electrolytic solution, and also they space treated through a buffered solution and heated later. The viscous gel is enabled to set on a glass plate or tube

Working that Salt Bridge

The oxidations that occur in anode create electron and also positive ions. Currently the electrons flow through the cable leaving the unbalanced positive charge in a beaker. In order to maintain the electric neutrality the negatively fee (NO3–) ion moves to the positively fee beaker (anodic half cell).


A similar situation establishes in the cathode cell yet in reverse. Right here the Cu2+ ions are consumed. For this reason for preserving the electrical neutrality, the K+ ions space migrated into this fifty percent cell indigenous the salt bridge. Hence, the electrical neutrality of the systems is kept using the salt bridge.

What wake up if No Salt leg is supplied in a Galvanic Cell?

A galvanic cell is one where electrical energy is generated by a oxidation reaction. A salt leg plays an important role in a galvanic cell. Let us see what wake up if there is no salt bridge present in the galvanic cell.

Before wires are connected, the equipment in each beaker is neutral.So they have actually an equal number of positive fees and negative charges.The zinc bar (Anode supplied in a galvanic cell) will provide up 2 electrons. So the the electrons flow to the copper bar (cathode used in the galvanic cell) v the wire.So the systems gains a hopeful charge since zinc loser electrons.The copper bar (cathode) takes the two electrons leading to one optimistic copper ion (Cu+2) to leave the solution and accept the 2 electrons.When this happens an atom of copper will deposit ~ above the copper bar.Hence, this systems becomes negative charged.

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Now there exist two voltages, one between the electrodes (metal bar) and the various other is in between the charged solutions. The voltage in between the metal bar or electrode is positive and also the voltage between the charged equipment is negative. So this voltages will certainly cancel out and also no current will flow. This proves the prominence of salt bridges in any electrochemical cell or electrolysis.