Silver Chloride - AgCl

Silver chloride is described as a white crystalline chemical compound having the formula AgCl. Silver chloride, present in the test tube, turns purplish quickly, especially in the case of a sunny laboratory due to the silver chloride being split up into both chlorine and silver. Silver chloride can be prepared when the sodium chloride compound is added to the silver nitrate solution; there occurs a white precipitate of silver chloride. Silver chloride is also an example of a well-known salt stain, which is used to impart an amber colour to the glass. Chloro silver is the other name of silver chloride.

Properties of Silver Chloride

Let us look at the properties of silver chloride as follows.

Physical Properties of Silver Chloride – AgCl

Let us look at the physical properties of silver chloride.

Chemical Properties of Silver Chloride – AgCl

Let us look at the chemical properties of silver chloride.

• Silver chloride undergoes a decomposition reaction in the presence of sunlight to produce chlorine and silver. The chemical reaction for the same can be given as follows:

AgCl → Ag + Cl

• Silver chloride reacts with a base same as ammonia, forming a complex compound known as chloride ion and Silver diammo ion. The chemical reaction for the same can be given as follows:

AgCl + 2NH3 → [Ag(NH3)2]+ + Cl–

Silver Chloride Structure

The solid adopts the structure of fcc NaCl, where every Ag+ ion is surrounded by an octahedron of 6 chloride ligands. Similarly, AgBr and AGF crystallize. However, crystallography depends on the crystallization condition, majorly in the free silver ion concentration.

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Preparation of Silver Chloride

Silver chloride is given as unusual, where in that, unlike most of the chloride salts, it contains very low solubility. It can be synthesized easily by the process of metathesis, which is combining an aqueous solution of silver nitrate (soluble) with a soluble chloride salt, like cobalt(II) chloride or sodium chloride. The formed silver chloride will precipitate immediately.

Uses of Silver Chloride

Let us look at the important uses of silver chloride as listed below.

• In electrochemistry, the silver chloride electrode is described as a common reference electrode.

• Silver chloride's low solubility makes it a useful addition to pottery glazes for the formation of "Inglaze lustre".

• It has been used as an antidote for mercury poisoning, assisting in mercury elimination.

Silver chloride is Also Used:

• To make a photographic paper because it reacts with photons to produce a latent image via photoreduction

• In the photochromic lenses, again taking advantage of its reversible conversion to Ag metal

• Wound healing products and in bandages

• To create amber, brown, and yellow shades in the manufacturing of stained glass

• As an infrared transmissive optical component since it can be hot-pressed into lens shapes and window

As an Antimicrobial Agent:

• For the long-term preservation of drinking water in water tanks

• In a few personal deodorant products

Why is Silver Chloride Soluble in Ammonia and Silver Iodide is Insoluble in Ammonia?

Due to the dissociation constant, if we notice the rows of the periodic table, chlorine falls above the iodine which means, it makes stronger ions, and we also know that strong ions contain high dissociation. Moreover, higher dissociation is also known as higher reactivity. Another way to look at it is from the acid-base point of view.

The base of silver is weak, whereas chlorine acid is strong. When the weak base reacts with a strong acid, it forms acidic salt. It means the salt that produces acidic ph, currently (ammonia), becomes a base when dissolved in water. Thus, chlorine from AgCl reacts with NH₃ to produce NH₄-Cl. Even though the AgCl holds a poor dissociation, the ionized Cl reacts with ammonia and disturbs the equilibrium present between Ag+and Cl-. Hence, more AgCl dissociates to maintain the equilibrium until all the Agcl is consumed.

Furthermore, the acid of iodine and the silver base is weak. Therefore, weak acid reacts with the weak base to form neutral salt with poor dissociation. We can also confirm it by the fact that the solubility of AgI is poorer than the AgCl.

Is AgCl Insoluble in Water?

No, though AgCl and NaCl seem to be similar, the Ag ion's effective nuclear charge is much more compared to the Na+ ion. Thus, according to the Fajan law, it polarizes chloride anion and forms the bond between them more covalently (in NaCl, Na holds an overall positive charge, and chloride holds a negative charge. Hence, there is no electron present between Cl and Na, and thus it is not covalent. Whereas in Cl and Ag, as polarization occurs, the electron residing on Cl^- gets towards the Ag⁺ ion. Therefore, some amount of electric charge comes between Cl^- and Ag⁺ ion and this forms a covalent bond.

Use of Silver Chloride as Electrode

Silver Chloride is considered a convenient option to be used as a reference electrode. In electrochemistry,  the industry uses two types  of electrodes to make potential measurements. 

One type of electrode is called the indicator electrode which has a particular characteristic that allows the electrode to selectively respond to changes in activity of the analyte being measured. On the other end, a reference electrode is needed in the system that possesses a characteristic which allows it to remain stable to the changes in the activity of the analyte being measured. In order for potential measurements to have context, the reference electrode needs to be composed in a manner that it remains stable over time to potential changes being measured whereas the indicator electrode responds reactively.

The silver chloride reference electrode is made up of a silver wire coated with a layer of solid silver chloride submerged in a solution saturated with potassium chloride and silver chloride.

Silver Chloride as Electrolyte

Silver chloride is considered a strong electrolyte. Silver chloride is one of the few insoluble ionic compounds that are strong electrolytes. There is virtually no undissociated form of the silver chloride compound in the solution as even if small amounts dissolve in water, they do so as ions only.

Get Silver Chloride from Sodium Chloride

In a double displacement reaction between aqueous silver nitrate solution and aqueous sodium chloride solution, silver chloride and sodium nitrate are formed. Silver nitrate solution and sodium chloride solution are both colourless solutions. These solutions upon reaction with each other produce a white precipitate and a colourless solution. The resultant solution is sodium nitrate. The resultant precipitate is silver chloride.

Then resulting compounds, silver chloride and sodium nitrate do not react with each other. Silver chloride can be separated from sodium nitrate by adding water to the solution to dissolve sodium nitrate because it is soluble in water whereas the silver chloride precipitate is not soluble in water. Hence, silver chloride can be obtained through separation and filtration. 

Students can learn more about such chemical reactions to obtain certain  compounds for use in real life applications on Vedantu. Study material on most types of chemical compounds, their unique physical and chemical properties, reactions with other compounds and their industry use are available to students to download for free from the Vedantu website and app for exam preparation and revision.

Separate Silver Chloride from Water

As silver chloride is a white solid compound which is not soluble in water, the two can be easily separated through the filtration technique if the mixture is passed through a filter paper. The white precipitate stuck on the filter paper as residue is silver chloride. The filtrate collected in the beaker at the bottom of the filter paper is water. This water can be distilled to achieve purity.

Distillation to purify water is a process that relies on evaporation and condensation. Contaminated water is heated to form steam, whereas molecular compounds like silver chloride do not get evaporated and are left behind. Then, the steam cools down to condense in the form of pure water droplets collected separately.