Precipitation is the creation of a solid from a solution. Initially, the reaction occurs in a liquid state, after which a certain substance is formed, which is called a “precipitate”. The chemical component that causes its formation has the scientific term “precipitant”. Without sufficient gravity (settling) to bring hard particles together, the sediment remains in suspension.
After sedimentation, especially when using a centrifuge for pressing into a compact mass, the precipitate can be called a “granule”. It can be used as a medium. The liquid remaining over the solid without precipitation is called the “supernatant”. Precipitation is powders obtained from residual rocks. They were also historically known as “flowers.” When a solid appears in the form of chemically treated cellulose fibers, this process is often called regeneration.
Element solubility
Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction. If precipitation from silver nitrate solutions is poured into sodium chloride liquid, chemical reflection occurs with the formation of a white precipitate from a precious metal. When liquid potassium iodide reacts with the substance of lead (II) nitrate, a yellow precipitate of lead (II) iodide is formed.
Precipitation can occur if the concentration of the compound exceeds its solubility (for example, when mixing various components or changing their temperature). Complete precipitation can occur quickly only from a supersaturated solution.
In solids, the process occurs if the concentration of one product is above the solubility limit in the other host body. For example, due to rapid cooling or ion implantation, the temperature is high enough so that diffusion can lead to the separation of substances and the formation of a precipitate. Complete deposition in solids is commonly used for the synthesis of nanoclusters.
Supersaturation
An important step in the deposition process is the beginning of nucleation. The creation of a hypothetical solid particle involves the formation of an interface, which, of course, require some energy based on the relative surface motion of both the solid and the solution. If a suitable nucleation structure is not available, a glut occurs.
Precipitation example: copper from a wire that is forced out by silver into a solution of metal nitrate, into which it is dipped. Of course, after these experiments, solid material precipitates. Precipitation reactions can be used to produce pigments. And also for the removal of salts from water during its processing and in classical qualitative inorganic analysis. This is how copper is deposited.
Porphyrin crystals
Precipitation is also useful during the isolation of reaction products when processing occurs. Ideally, these substances are insoluble in the reaction component.
Thus, a solid precipitates as it forms, preferably creating pure crystals. An example of this is the synthesis of porphyrins in boiling propionic acid. When the reaction mixture is cooled to room temperature, crystals of this component fall to the bottom of the vessel.
Precipitation may also occur when an anti-solvent is added, which drastically reduces the absolute water content of the desired product. After this, the solid can be easily separated by filtration, decantation or centrifugation. An example is the synthesis of chromium chloride tetraphenylporphyrin: water is added to the reaction solution of DMF, and the product precipitates. Precipitation is also useful in the purification of all components: untreated bdim-cl completely decomposes in acetonitrile and is discharged into ethyl acetate, where it precipitates. Another important use of the anti-solvent is the deposition of ethanolysis of DNA.
In metallurgy, solid solution deposition is also a useful method of alloy hardening. This decay process is known as strengthening a solid component.
Representation using chemical equations
Example precipitation reaction: aqueous silver nitrate (AgNO 3) is added to a solution containing potassium chloride (KCl), a decomposition of a white solid, but already silver (AgCl), is observed.
He, in turn, formed a steel component, which is observed as a precipitate.
This precipitation reaction can be written with emphasis on dissociated molecules in the combined solution. This is called the ionic equation.
The last way to create such a reaction is known as pure bond.
Precipitation of various colors
Green and reddish-brown spots on the limestone core sample correspond to the solids of oxides and hydroxides Fe 2+ and Fe 3+.
Many compounds containing metallic ions produce precipitates with distinctive colors. The following are typical shades for various metal depositions. However, many of these compounds can produce colors that are very different from those listed.
Other associations usually form white precipitation.
Anionic and cationic analysis
Precipitation is useful in detecting the type of cation in the salt. To do this, the alkali first reacts with an unknown component to form a solid. This is the precipitation of the hydroxide of a given salt. To identify the cation, the color of the precipitate and its solubility in excess are noted. Similar processes are often used in sequence - for example, a mixture of barium nitrate will react with sulfate ions to form a solid precipitate of barium sulfate, which indicates the likelihood that the second substances are present in abundance.
Digestion process
The aging of the precipitate occurs when the newly formed component remains in the solution from which it precipitates, usually at a higher temperature. This leads to cleaner and larger particle deposition. The physicochemical process that underlies digestion is called Ostwald ripening. Here, protein precipitation can be given as an example.
This reaction occurs when cations and anions in a hydrophytic solution combine to form an insoluble heteropolar solid element called a precipitate. Whether such a reaction takes place or is absent, it is possible to establish by applying the principles of water content for common molecular solids. Since not all aqueous reactions form precipitates, it is necessary to familiarize yourself with the solubility rules before determining the state of products and writing the total ionic equation. The ability to predict these reactions allows scientists to determine which ions are present in solution. It also helps industrial enterprises to form chemicals by extracting components from these reactions.
Properties of various precipitation
They are insoluble ionic solid reaction products formed when certain cations and anions are combined in an aqueous solution. Determinants of sludge formation may vary. Some reactions are temperature dependent, for example, the solutions used for buffers, while others relate only to the concentration of the solution. The solids formed in the precipitation reactions are crystalline components and can be suspended in the entire liquid or fall to the bottom of the solution. The remaining water is called the supernatant. Two elements of consistency (sediment and supernatant) can be distributed by different methods, such as filtration, ultracentrifugation or decantation.
The interaction of deposition and double substitution
Applying solubility laws requires an understanding of how ions react. Most of the precipitation interactions are a single or double substitution process. The first option occurs when two ionic reagents dissociate and bind to the corresponding anion or cation of another substance. Molecules replace each other based on their charges in the form of a cation or anion. This can be seen as a “switch partners." That is, each of the two reagents “loses” its companion and forms a bond with the other, for example, chemical deposition of hydrogen sulfide occurs.
The double substitution reaction is specifically classified as a hardening process when the chemical equation in question arises in an aqueous solution and one of the resulting products is insoluble. An example of such a process is given below.
Both reagents are aqueous and one product is solid. Since all components are ionic and liquid, they dissociate and therefore can completely dissolve in each other. However, there are six principles of water content that are used to predict which molecules are insoluble when precipitated in water. These ions form a solid precipitate in a common mixture.
Solubility rules, deposition rate
Is the precipitation reaction a dictated rule for the water content of substances? In fact, all these laws and conjectures provide guidelines that tell which ions form solids and which remain in their original molecular form in aqueous solution. Rules must be followed from top to bottom. This means that if something is unsolvable (or solvable) due to the first postulate, it takes precedence over the following instructions with a higher serial number.
Bromides, chlorides and iodides are soluble.
Salts containing precipitation of silver, lead and mercury cannot be completely mixed.
If the rules indicate that the molecule is soluble, then it remains in aqueous form. But if the component is immiscible in accordance with the laws and postulates described above, then it forms a solid with an object or liquid from another reagent. If it is shown that all ions in a reaction are soluble, then the deposition process does not occur.
Pure ionic equations
To understand the definition of this concept, it is necessary to recall the law for the double substitution reaction, which was given above. Since this particular mixture is a precipitation method, states of matter can be assigned to each variable pair.
The first step to writing a pure ionic equation is to separate soluble (aqueous) reagents and products into their respective cations and anions. Precipitation does not dissolve in water, so the solid should not be separated. The resulting rule is as follows.
In the above equation, A + and D - ions are present on both sides of the formula. They are also called spectator molecules because they remain unchanged throughout the reaction. Since it is they who go through the equation without changes. That is, they can be excluded to show the formula of a perfect molecule.
The pure ionic equation shows only the precipitation reaction. A network molecular formula must be balanced on both sides, not only from the point of view of the atoms of the elements, but also if we consider them from the side of the electric charge. Precipitation reactions are usually represented solely by ionic equations. If all products are aqueous, a pure molecular formula cannot be written. And this happens because all ions are excluded as products of the viewer. Therefore, no precipitation reaction naturally occurs.
Applications and examples
Precipitation reactions are useful in determining whether the same essential element is present in a solution. If a precipitate is formed, for example, when a chemical reacts with lead, the presence of this component in water sources can be verified by adding a chemical and controlling the formation of sediment. In addition, deposition reflection can be used to extract elements, such as magnesium, from seawater. Precipitation reactions even occur in the human body between antibodies and antigens. However, the environment in which this happens is still being studied by scientists from around the world.
First example
It is necessary to complete the double substitution reaction, and then reduce it to the equation of a pure ion.
First, it is necessary to predict the final products of this reaction, using knowledge of the double-exchange process. To do this, remember that cations and anions “switch partners”.
Secondly, it is worth dividing the reagents into their full-fledged ionic forms, since they exist in an aqueous solution. And also do not forget to balance both the electric charge and the total number of atoms.
Finally, you need to include all the ions of the viewer (those same molecules that are found on both sides of the formula that have not changed). In this case, these are substances such as sodium and chlorine. The final ionic equation looks like this.
It is also necessary to complete the double substitution reaction, and then, again, be sure to reduce it to the equation of a pure ion.
General Problem Solving
The predicted products of this reaction are CoSO4 and NCL from the rules of solubility, COSO4 completely decomposes, because paragraph 4 states that sulfates (SO2-4) do not settle in water. In the same way, one must find that the NCL component is solvable on the basis of postulate 1 and 3 (only the first passage can be cited as evidence). After balancing, the resulting equation has the following form.
For the next step, it is worth splitting all the components into their ionic forms, since they will exist in an aqueous solution. And also balance the charge and atoms. Then cancel all the ions of the viewer (those that appear as components on both sides of the equation).
No precipitation reaction
This specific example is important because all reagents and products are aqueous, which means that they are excluded from the pure ionic equation. There is no solid precipitate formed. Therefore, no precipitation reaction occurs.
It is necessary to write the total ionic equation for potentially double displacement reactions. It is definitely worthwhile to include the state of matter in the solution, this will help achieve balance in the general formula.
Solutions
1. Regardless of the physical condition, the products of this reaction are Fe (OH) 3 and NO3. Solubility rules predict that NO3 completely decomposes in a liquid because all nitrates are so (this is proved by the second point). Nevertheless, Fe ( ) 3 is insoluble, because the precipitation of hydroxide ions always has this form (the sixth postulate can be used as evidence) and Fe is not one of the cations, which leads to the exclusion of the component. After dissociation, the equation has the following form:
2. As a result of the double substitution reaction, the products are Al, CL3 and Ba, SO4, AlCL3 is soluble because it contains chloride (rule 3). However, B a S O4 does not decompose in a liquid, since the component has sulfate in its composition. But B 2 + ion also makes it insoluble, because it is one of the cations that causes an exception to the fourth rule.
This is what the final equation looks like after balancing. And when removing spectator ions, the following network formula is obtained.
3. From a double substitution reaction, products of HNO3 as well as ZnI2 are formed. According to the rules, HNO3 decomposes because it contains nitrate (second postulate). And Zn I2 is also soluble, because iodides are the same (paragraph 3). This means that both products are aqueous (that is, dissociate in any liquid) and thus no precipitation reaction occurs.
4. The products of this double substitutional reflection are C a3 (PO4) 2 and N CL. Rule 1 states that N CL is soluble, and according to the sixth postulate, C a3 (PO4) 2 does not decompose.
It is this form that the ionic equation will have when the reaction is complete. And after the exclusion of precipitation, this is the formula.
5. The first product of this reaction, PbSO4, is soluble in accordance with the fourth rule, because it is sulfate. The second KNO3 product also decomposes in the liquid because it contains nitrate (second postulate). Therefore, no precipitation reaction occurs.
Chemical process
This action of separating a solid during precipitation from solutions occurs either by converting the component into a non-decaying form, or by changing the composition of the liquid to reduce the quality of the object in it. , , , , .
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To affect the decomposition of substances in the compound, a precipitate is necessary with the formation of an insoluble compound, either created by the interaction of two salts or by changing the temperature.
This deposition of ions may indicate that a chemical reaction has occurred, but it can also happen if the concentration of the solute exceeds its fraction of total decomposition. The action precedes an event called nucleation. When small insoluble particles aggregate with each other or form the upper part of the interface with the surface, such as the wall of the container or the seed crystal.
Key findings: determination of precipitation in chemistry
In this science, this component is both a verb and a noun. Precipitation is the formation of some insoluble compound, either by reducing the total decomposition of the combination, or through the interaction of two salt components.
A solid has an important function. Since it is formed as a result of the precipitation reaction, it is called a precipitate. A solid is used to clean, remove or recover salts. And also for the manufacture of pigments and the identification of substances in a qualitative analysis.
Precipitation against deposition, conceptual apparatus
The terminology may seem a bit confusing. Here's how it works: the formation of a solid from a solution is called sediment. And the chemical component that arouses hard decomposition in the liquid state is called a precipitant. If the particle size of the insoluble compound is very small or the gravity is insufficient to draw the crystalline component to the bottom of the container, the precipitate can be evenly distributed throughout the liquid, forming a suspension. Sedimentation refers to any procedure that separates the precipitate from the aqueous portion of the solution, which is called the supernatant. A common sedimentation method is centrifugation. Once the precipitate is recovered, the resulting powder can be called a “flower”.
Another example of communication
Mixing silver nitrate and sodium chloride in water will cause silver chloride to precipitate out of solution as a solid. That is, in this example, the precipitate is a cholesterol.
When writing a chemical reaction, the presence of precipitation can be indicated by the following scientific formula with a down arrow.
Precipitation use
These components can be used to identify a cation or anion in a salt as part of a qualitative analysis. It is known that transition metals form different precipitation colors depending on their elemental identity and oxidation state. Precipitation reactions are mainly used to remove salts from water. And also for the selection of products and for the preparation of pigments. Under controlled conditions, the precipitation reaction produces pure precipitate crystals. In metallurgy, they are used for hardening alloys.
How to recover sediment
There are several precipitation methods used to extract solids:
- Filtration. With this action, the solution containing the precipitate is poured onto the filter. Ideally, a solid remains on the paper, and liquid passes through it. The container can be rinsed and poured onto a filter to aid recovery. There is always some loss, either due to dissolution in the liquid, passage through the paper, or due to adhesion to the conductive material.
- Centrifugation: with this action, the solution rotates rapidly. For the technique to work, the solid sediment must be more dense than the liquid. The densified component can be obtained by pouring out all the water. Typically, losses are less than with filtration. Centrifugation works well with small sample sizes.
- Decantation: with this action, the liquid layer is poured out or sucked off from the sediment. In some cases, an additional solvent is added to separate the water from the solid. Decantation can be used with the entire component after centrifugation.
Precipitation aging
A process called digestion occurs when a fresh solid is allowed to remain in its solution. Typically, the temperature of the entire fluid rises. Improvised digestion can produce larger particles with high purity. The process that leads to this result is known as Ostwald ripening.