Introduction to Precipitation Reaction
During a Chemical reaction, chemical changes occur that lead to the formation of new compounds under some specific conditions. Chemical equations are a very important tool that can help us in understanding the chemical reactions between two or more elements or compounds. Interaction of reactants and the products that are involved in a chemical reaction is displayed in the chemical equations. Various compounds during the chemical reaction will interact with each other and are called reactants. These reactants can be in any state - solid, gaseous, or liquid.
Overview of Precipitation Reaction
We see many chemical reactions in our day to day lives. Some of the most common examples of chemical reactions are burning, corrosion, cooking of food and digestion etc. Keeping this in mind, let us talk about Precipitation reactions; in these reactions, by combining two different soluble salts in an aqueous state, two different products were formed. One formed product is insoluble in the solution and is thus precipitated out. Therefore, it is referred to as the 'precipitate.’
Precipitation Reaction – Definition and Meaning
A chemical reaction that takes place in an aqueous solution where two ionic bonds combine and an insoluble salt is precipitated out as a byproduct is called the precipitation reaction. The insoluble salts that are formed in precipitation reactions are called precipitates. Precipitation reactions are an example of double displacement reactions in which a solid form residue called the precipitate is left behind. When two or more two solutions containing different salts are combined, insoluble salts are produced that precipitate out of the solution.
The chemical reaction between potassium chloride (KCl) and silver nitrate (AgNO3), in which solid silver chloride is precipitated out of the solution, is one of the most common examples of precipitation. It is the insoluble salt formed as a product of the precipitation reaction. The chemical equation is given below :
\[ AgNO_{3}(aqueous) + KCl(aqueous) \rightarrow AgCl(precipitate) + KNO_{3}(aqueous) \]
In the above reaction, silver chloride, which is a white colour solid-state precipitate, is formed, which is insoluble in nature. This solid silver chloride is precipitated out because of its insolubility in water. Precipitation reactions play a key role in determining the presence of different ions in a particular solution.
Another example of a precipitation reaction is the reaction between calcium chloride (CaCl2) and potassium hydroxide (KOH), which results in the formation of an insoluble salt known as calcium hydroxide. The chemical equation is given below :
\[ 2KOH(aqueous) + CaCl_{2}(aqueous) \rightarrow Ca(OH)_{2}(aqueous) + 2KCl(aqueous) \]
Some more examples of precipitation reaction with their chemical equations are given below:
\[ AgNO_{3} + NaCl \rightarrow AgCl \downarrow + NaNO_{3} \]
\[ Mg(OH)_{2}(s) + 2HCl \rightarrow MgCl_{2} + 2H_{2}O(l) \]
A precipitation reaction is a kind of chemical reaction in which two soluble salts in a fluid solution mixes and one of the items is an insoluble salt called a precipitate. The precipitate stays in the solution as a barrier, or it can also be removed from the liquid by using the process of centrifugation, decantation or filtration. Most of the other salts are insoluble except calcium, barium etc.
Precipitation reactions are generally single replacement reactions or double replacement reactions. In a double substitution reaction, both ionic reactants separate in water. For a double replacement reaction to be a precipitation reaction, one of the items must be insoluble in the liquid solution.
Precipitation Example
Silver nitrate and potassium chloride is a precipitation reaction because solid silver chloride is formed as a product of the reaction.
\[ AgNO_{3}(aq) + KCl(aq) \rightarrow AgCl(s) + KNO_{3}(aq) \]
The reaction could be seen as a precipitation reaction because 2 ionic liquid solutions react to a form a solid product.
When a precipitation reaction is written in the terms of ions in the solution, it is known as ionic equations.
\[ Ag^{+} (aq) + NO^{3-}(aq) + K^{+} (aq) + Cl^{−} (aq) \rightarrow AgCl (s) + K^{+} (aq) + NO^{3−}(aq) \]
Net ionic equations are another way to write a precipitation reaction. In a net ionic equation, the ions that don't take part in the precipitation are left out. These ions are called spectator ions. In this example, the net ionic equation is
\[ Ag^{+} (aq) + Cl^{−} (aq) \rightarrow AgCl (s) \]
Uses of Precipitation
Precipitation can be used to separate the cation or anion, a soluble salt. These reactions are used to remove salt from the water and to segregate items. Under controlled conditions, a precipitation reaction produces unadulterated stones. In metallurgy, precipitation is used to reinforce combinations of metals.
Precipitation reactions help in determining a particular component in a given solution.
Precipitation reactions can be used in wastewater treatment. In wastewater treatment, many metals can be discovered, for instance: mixers of sulphate and hydroxide.
3 Ways of Recovering a Precipitate
Filtration: In the filtration process, the mixture of the precipitate is poured over a funnel. In perfect condition, the precipitate stays on the funnel while the fluid goes through it. The holder may be flushed and poured onto the channel to help recover.
Centrifugation: In centrifugation, the mixture is quickly rotated. The solid precipitate must be thicker than the fluid. The compressed precipitate, called the pellet, can be recovered by pouring off the fluid. There is normally less misfortune than with filtration.
Decantation: In decantation, the fluid layer is poured or suctioned far from the precipitant. Repeatedly, an extra soluble particle is added to separate the mixture from the precipitant.
Properties of Precipitates
Precipitates are insoluble ionic solid results of a reaction, formed when certain cations and anions join in a watery solution. The determining element of the solution of a precipitate can change. A few reactions rely upon temperature, such as the solution used for buffers, whereas others rely just on the solution concentration. The solids created in precipitation reactions are crystalline solids, which can be suspended throughout the fluid or settle to the base of the solution. The left-out liquid is called supernatant liquid. The two segments of the mixture (precipitate and supernate) can be separated by different techniques, for example, filtration, centrifuging, or decanting.
Both reactants are liquid and one product is solid. Because the reactants are ionic and liquid, they separate and are therefore soluble. However, there are six solubility rules used to forecast which particles are insoluble in water. These particles form a solid precipitate in solution.
Properties of the Precipitation Reaction and its Precipitates
Some of the properties of Precipitation Reaction and its precipitates are given below:
The precipitation reaction can only take place in an aqueous solution or medium in an ionic state.
The reaction takes place between ions that are present in the aqueous solutions, forming the product.
The products of the precipitation reaction are the precipitates that are insoluble in the given aqueous solutions.
Precipitation reactions are ionic in nature since the ions actively take part in the reaction and form the product.
Like any other chemical reaction, these reactions also depend on the temperature, concentration of the solution, buffer solution, etc.
Precipitation and Double Replacement Reactions
Most precipitations are single replacement reactions or double replacement reaction. A double replacement reaction happens when two ionic reactants separate and bond with the individual anion or cation from the other reactant. The particles replace each other depending on their charges as either a cation or an anion.
Double Replacement Reaction:
A double replacement reaction is particularly classified as a precipitation reaction when the chemical equation occurs in liquid solution and one of the products formed is insoluble. An example of a precipitation reaction is given beneath:
\[ CdSO_{4} (aq) +K_{2}S(aq) \rightarrow CdS(s)+K_{2}SO_{4}(aq) \]
Solubility Rules
Regardless of whether a reaction results a precipitate is depended on the solvability rules. These principles show us which particles change into solids, and which stay in their ionic structure in the liquid solution. These principles are to be followed starting from the top, implying that if something is insoluble (or soluble) because of rule 1, it has priority over a higher-numbered rule.
1. Salts formed with rule 1 cation and NH4+ cations are soluble. There are a few special cases for certain Li+ salts.
2. Acetates (C2H3O2-) nitrates (NO3-) and perchlorates (ClO-4 ) are dissolvable.
3. Bromides and iodides are soluble.
4. Sulphates (SO2-4 ) are dissolvable except for sulphates with Ca2+, Sr2+, and Ba2+.
5. Salts containing silver, lead, and mercury is not soluble.
6. Carbonates (CO2-3), phosphates (PO3-4) sulfides, oxides, and hydroxides (OH-) are insoluble. Sulphides made with rule 2 cations and hydroxides formed with calcium, strontium, and barium are special cases.
Net Ionic Equations
To comprehend the meaning of a net ionic condition, review the condition for the double replacement reaction. Since this specific reaction is a precipitation reaction, states of matter can be delegated to every variable pair:
\[ AB(aq) + CD(aq) \rightarrow AD(aq) + CB(s) \]
The initial step to composing a net ionic condition is to separate the soluble (watery) reactants and particles into their individual cations and anions. Precipitates don't separate in water, so the solid shall not be separated. The subsequent condition is shown below:
\[ A^{+}(aq) + B^{-}(aq) + C^{+}(aq) + D^{-} (aq) \rightarrow A^{+}(aq) + D^{-}(aq) + CB(s) \]
In the condition above, A+ and D- particles are available on the two sides of the condition. These are called observer particles since they stay unchanged throughout the reaction. Since they experience the condition unaltered, they can be wiped out to demonstrate the net ionic condition:
\[ C^{+} (aq) + B^{-}(aq) \rightarrow CB (s) \]
Examples:
1. Complete the double replacement reaction and after that reduce it to the net ionic condition.
\[ NaOH (aq) + MgCl_{2} (aq) \rightarrow \]
To start with, foresee the results of this reaction utilizing the knowledge of double replacement reactions.
Second, counsel the solubility principles to decide whether the items are soluble. Rule 1 cations (Na+) and chlorides are dissolvable from principles 1 and 3 separately, so NaCl will be soluble in water. In any case, rule 6 expresses that hydroxides are insoluble, and in this way Mg(OH)2will shape a precipitate. The subsequent equation is the following:
\[ 2NaOH (aq) + MgCl_{2} (aq) \rightarrow 2NaCl (aq) + Mg(OH)_{2} (S) \]
Third, separate the reactants into their ionic structures, as they would exist in a watery solution. Make sure that you adjust both the electrical charge and the number of molecules:
\[2Na^{+}(aq)+2OH^{-}(aq)+Mg^{2+}(aq)+2Cl^{-}(aq) \rightarrow Mg(OH)_{2}(S)+2Na^{+} (aq) + 2Cl^{-}(aq) \]
Finally, kill the observer particles (the particles that occur on the two sides of the equations unaltered). For this situation, they are the sodium and chlorine particles. The last net ionic condition is:
\[ Mg^{2+} (aq) + 2OH^{-}(aq) \rightarrow Mg(OH)_{2}(S) \]
Applications of Precipitation Reaction
Precipitation reactions are very helpful in determining the presence of a particular element in a given solution. These reactions also govern the formation of a precipitate when some chemical is added to the solution. A precipitation reaction is used for the extraction of magnesium from salty seawater. These reactions also take place inside the human body as the reactions that occur between antigens and antibodies.
Examples of Precipitation Reaction in Everyday Life
The treatment of wastewater from our houses and industries can be done using precipitation reactions. When a contaminant forms an insoluble solid with the solution, then we can use this reaction to precipitate out the contaminated ions from it. Wastewater consists of heavy metals in large amounts; a frequent presence of heavy metals such as compounds of sulphide and hydroxide can be found. So, adding a source of hydroxide will result in a precipitation reaction because of its solubility.
FAQs on Precipitation Reaction
1. What is precipitation reaction?
Precipitation reaction can be defined as "a chemical reaction that takes place in an aqueous solution where two ionic bonds combine, and an insoluble salt is precipitated out as a byproduct". The insoluble salts that are formed in precipitation reactions are called precipitates. Precipitation reactions are an example of double displacement reactions in which a solid form residue called the precipitate is left behind. A precipitation reaction also occurs when two or more solutions combined with different salts result in the formation of insoluble salts that precipitate out of the solution.
2. What is a chemical reaction?
A chemical reaction can be defined as a process in which one or more substances which are known as the reactants, are converted to one or more different substances that are known as the products. Substances are either chemical elements or compounds having different properties. In a chemical reaction, the constituent atoms of the reactants are rearranged to create different substances as products. Examples of Chemical reactions are burning of paper, rusting of iron, cooking and digestion of food etc.
3. What are the applications of precipitation reaction?
Precipitation reactions have various applications in our day to day life. Precipitation reactions are very helpful in determining the presence of a particular element in a given solution. These reactions also govern the formation of a precipitate when some chemical is added to the solution. A precipitation reaction is used for the extraction of magnesium from salty seawater. These reactions also take place inside the human body as the reactions that occur between antigens and antibodies. Sometimes the pipes in our houses and buildings get clogged because precipitates of magnesium and calcium oxides have deposited themselves within the pipes.
4. What are precipitates in a chemical reaction?
A precipitate is an insoluble solid that emerges from an aqueous solution. The emergence of this insoluble solid from the given solution is called precipitation. The precipitate usually comes out in the form of a suspension. Precipitates can form one or more insoluble products when two soluble salts react in a solution.
First soluble salt + Second soluble salt → insoluble salt after precipitation
When the temperature of a solution becomes low, precipitates will form. Low temperature may result in their precipitation as solids during a reaction because of the solubility of salts.
