Category: Chemistry Notes PPT

An electrolytic cell is a device that utilizes electrical energy to decompose some chemical compounds by a process known as Electrolysis. The electrolytic cell is nothing but a special kind of electrochemical cell. Ex: When water undergoes electrolysis, it breaks into hydrogen and oxygen. Here some additional energy is required to overcome the threshold energy barrier.

 

Voltaic cells are driven by a spontaneous chemical reaction that produces an electric current through an external circuit. These cells are essential because they are the basis for the batteries that fuel modern society. However, they are not the only kind of electrochemical cell. Non-spontaneous reactions usually require electrical energy to operate.

 

The general form of the reaction can be written as:

 

Reactants ⇌ Products – Electrical Energy Spontaneous⟶⟵Non-spontaneous (1)

 

Electrolytic cell is a device through which conversion of electrical energy is done to chemical energy or it can be vice versa. These types of cells usually comprise two electronic or metallic conductors also known as electrodes and these are held apart or remain in the contact of an electrolyte (q.v.), generally a fused or dissolved ionic compound.

 

Connection of all these electrodes with the support of the source of the direct electric current is one of them and it remains negatively charged (cathode) or the other one is positively charged. These come together with one or more electrons that come along and a part of their charge is lost by the charge and it becomes ions with neutral atoms or lower charge or it might be molecules at that particular time. 

 

Negative ions transfer the positive anode (electrode) and transmit one as well as more electrons in it. This comes out as fresh neutral or ions particles. The whole effect of these two processes happens as per the transmission of the electrons. has provided a detailed explanation of the term so that the students are able to understand it thoroughly and they can attempt the questions based on it without a hassle.

 

Galvanic Cell and Electrolytic Cell Comparison

Electrolytic cells are those which work on chemical energy by utilizing electrical power from the system. The electrolytic cells work on a similar mechanism as that of the Galvanic cells. Both the cells mainly consist of two half cells, such as the oxidation half cell and redox half cell. However, the flow of electrons is a little different. Still, the cathode and anode definition remains the same, where reduction takes place at the cathode and oxidation occurs at the anode. Because both half-reactions’ directions have been reversed, the sign, but not the magnitude, of the cell potential has been changed.

 

Electrolytic cells are very similar to voltaic (galvanic) cells because both require a salt bridge, both have a cathode and anode side, and both have a consistent flow of electrons from the anode to the cathode. However, there are also striking differences between the two cells. The main differences are outlined below:

 

has compared electrolytic and galvanic cells as these two sometimes comprise a single question based on the comparison or you can also get short notes on them separately. Once the students are able to obtain comprehension, then they will be able to attempt the related questions if they are not related to the topics directly. After this simple comparison between these two, you can also get a question on hardcore difference, not an issue as is going to explain the difference for the students in the below paragraphs. So, your preparation will be strong enough, just hold the topic explained by in your mind thoroughly.

 

Difference Between Galvanic Cell and Electrolytic Cell

Electrolytic Cell

Let us take an example to understand clearly about Electrolytic cells. When molten Sodium chloride undergoes decomposition, it gets converted into metallic sodium and Chlorine gas.

 

[2Nacl rightarrow 2 Na + Cl_{2}]

 

If we put carbon electrodes with both ends c to the molten NaCl in a container, the electrolysis will occur when an additional energy source is applied. Electrons’ flow will take place from the anode and neutralize the Na+ ion at the cathode end.

 

[Na^{+} + e  rightarrow Na]

 

Note that the oxidation site is still the anode and the site of reduction is still the cathode, but the charge on these two electrodes is reversed. The anode is now positively charged and the cathode has a negative charge. The conditions under which the electrolyte cell operates are significant. The substance that is the strongest reducing agent (the substance with the highest standard cell potential value in the table) will undergo oxidation. The substance that is the strongest oxidizing agent will be reduced. If an aqueous sodium chloride solution were used in the above system, hydrogen would undergo reduction instead of sodium because it is a stronger oxidizing agent than sodium.

 

Electrolytic Cell Application

• Electrolytic cells are mainly involved in hydrogen gas and oxygen gas production by water utilization.

• In the metal extraction process, these are very helpful. Exp – Aluminium extraction from bauxite

• Electroplating is another feature of the electrolytic cell. This is the process in which a protective covering of a specific metal is done on another metal.

• Electrowinning is also another application in which metal extraction is done from the raw ore. The leeching phenomenon is generally followed in this process.

• To remove the impurities from the metal, the electrorefining method is followed.

• During heavy metals like copper, zinc, and aluminium and the highest purity level, electrolytic cells are used.

 

Properties of Galvanic and Electrochemical Cells

The galvanic cell converts chemical energy into electrical energy. An electrolytic cell can convert electrical energy to chemical energy. A salt bridge is a connecting link between the two sections that are placed in two different containers. Oxidation reaction takes place at the anode region and the redox reaction in the cathode region. The external cell provides the necessary electrons that enter via cathode and release via anode.

 

Working Principle of an Electrolytic Cell

Electrochemical cells are devi
ces based on the principle that when a chemical oxidation-reduction reaction occurs, electrons are being transferred from one chemical species to another. In a galvanic cell, the electrons are usually allowed to flow outside of the device in a circuit to operate some electrical device. In the other type of electrochemical cell, called an electrolytic cell, the reverse process occurs. Electrons in the form of an electric current are deliberately being pumped through the chemicals in the section to force an electric current oxidation-reduction reaction to take place. An example of an electrolytic cell is the setup used to decompose water into hydrogen and oxygen by electrolysis.

 

Conclusion

Hence, subject matter experts have described all the ins and outs of the electrolytic cells chapter. The prime aim of is always to make an addition to the knowledge of the students along with a promise to help them obtain great marks academically. With our notes, they are able to know what an electrolytic cell is, its definition, its application in varied sectors, its properties, and the working principles of electrolytic cells. So, if you are also eager to be a part of tuitions, then it is really simple with a few clicks of the mouse. All you need to access us via our website or you can simply download the mobile application. 

The elements that lie in the middle of Group II A and Group II B elements in the current periodic table are the d block elements. The d-block elements can also be referred to as the Transition Elements because they are elements that lie between the metals and non-metals of the periodic table.

Considering the periodic table d block elements, group 3 to 12 elements are referred to as d-block elements that present between p-block and s-block elements. Since these elements represent a transition or change in properties from the most electropositive s-block elements to less electropositive p-block elements, these are known as the transition elements.

These d block elements typically display metallic qualities like ductility and malleability, high values of electrical and thermal conductivity, and good tensile strength.

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Electronic Configuration

The electronic configuration of an element is characterized as an arrangement of orbital’s electrons. The s, p, d, and f are the four chief nuclear orbitals. These orbitals ought to be occupied by the number of electrons of the orbital and its energy level. We can arrange the four orbitals based on their energy level as s < p < d < f. As indicated by Aufbau’s principle, one of the most reduced energy orbitals ought to be first filled.

The s orbital can get two electrons, whereas the p, d, and f orbitals can separately hold 6, 10, and 14 electrons. The electronic configuration of these elements generally is (n-1) d 1–10 ns1–2. The (n–1) settles for the inward d orbitals, which may contain 1 to 10 electrons, and the peripheral ns orbital may have 1 or 2 electrons.

In the periodic table, the d block also includes the middle area marked by s and p blocks. The actual name “transition” is given to the elements of d-block simply due to their position amongst the p and s block elements. So, the d-orbitals of the penultimate energy level in their atoms get electrons leading to the respective three columns of the transition metals, that is, 3d, 4d, and 5d. Still, the fourth line of 6d is inadequate.

However, this speculation has a few special cases as a result of extremely low energy contrast between the ns and (n-1) d orbitals. Furthermore, half and totally filled arrangements of orbitals result in more stable moderately.

This figure’s (periodic table d block elements) outcome is mirrored in the electronic configurations of Cu and Cr in the 3d series. For instance, consider the instance of Cr, which has 3d54s1 rather than 3d44s2; the energy gap between the two sets (4s and 3d) of orbitals is less sufficient to anticipate electron entering the 3d orbitals. In the event of Cu, also, the configuration is 3d104s1, but not 3d94s2.

1st Series Electronic Configuration of d-Block Elements

So, we sum up the first-line transition external configuration elements as 4s23dn. We already know that chromium and copper don’t follow this example in any case. This is a result of a very lesser energy distinction between the 3d and 4s shell. Tentatively it is found that half and totally filled orbital arrangements are more stable.

On account of the elements such as copper and chromium, the energy contrast between the orbitals is much smaller. Thus, it can’t keep the electrons entering the d shell. The electronic configuration of d block elements in the advanced periodic table can be composed as displayed in the periodic table d block elements.

2nd Series Electronic Configuration of d-Block Elements

The d block elements electronic configuration in the second series can be given below.

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3nd Series Electronic Configuration of d-Block Elements

The d block elements electronic configuration in the third series can be given below.

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4th Series Electronic Configuration of d-Block Elements

The d block elements electronic configuration in the fourth series can be given below. Cd, Zn, and Hg have their orbitals totally filled both in their ground and common oxidation states. It can be represented as (n-1) d10 ns2. So, they are not called as transition elements.

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Position of Periodic Table d Block Elements

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The d block elements are filled by the columns 3 to 12 and can have atoms of elements with completely filled ‘d’ orbital. A transition metal defined by IUPAC is as “an element whose atom or its cations has a partially filled ‘d’ sub-shell.”

The Reason Behind the Colored d-Block Elements

The transition element compounds that are colored are related to somewhat incompletely filled (n-1) d orbitals. The transition metal particles having unpaired d-electrons experience electronic transition starting with just one d-orbital then onto the next. In the middle of this d-d transition phenomenon, the electrons ingest certain energy from the radiation and transmit the rest of energy coloured as light. The particle’s shade is the reciprocal of the shading consumed by it. Consequently, the coloured particle is framed due to the d-d transition which falls in the visible area for all transition components.

Chemistry is the study of various kinds of matter and its properties. All around us, we see various kinds of substances and materials. It is therefore imperative to classify and categorize them so that their properties can be easily studied, analyzed, and understood. The matter around us can be categorized into pure matter and impure matter. Pure substances are the ones that have a fixed chemical composition. Impure substances are the ones that can have varying compositions, and as such do not exhibit a fixed set of properties.

 

Pure substances can further be classified into elements and compounds. Impure substances are also called mixtures. Depending on their composition, they can further be classified into homogeneous and heterogeneous.

 

 

What is an Element?

In chemistry, an element is a substance that cannot be further broken down into a simpler substance by using common chemical methods. All matter is fundamentally composed of elements. To date, more than 119 elements have been discovered and many more are in the process of being discovered. Every element has a fixed place in the periodic table, depending on its properties.

 

The smallest entity of an element is called an atom. Atoms are highly unstable, therefore do not exist independently. They always tend to combine with other elements in order to attain stability. To represent an atom of an element, we use symbols. Every element has a fixed symbol. Some commonly used symbols of elements are listed below.

 

Commonly Used Symbols of Elements

 

Classification of Elements

Depending on the properties, elements can be classified into metals, nonmetals, and metalloids.

 

Metals are the elements that have the tendency of losing electrons in order to gain stability, that is, they exhibit electropositivity. The physical properties of metals include hardness, high tensile strength, luster, conductivity, high melting and boiling points, etc.

 

Examples include sodium, potassium, iron, calcium, magnesium, lead, tin, etc.

 

Non-metals are the elements that have the tendency of gaining electrons in order to gain stability, that is, they exhibit electronegativity. The physical properties of non-metals include brittleness, comparatively lower tensile strength, non-luster, non-conductivity or insulation, lower melting and boiling points, etc.

 

Examples include hydrogen, helium, chlorine, iodine, sulfur, phosphorus oxygen, etc.

 

Metalloids are the elements that have properties that are in between those of metals and nonmetals.

 

Examples include boron, silicon, arsenic, antimony, germanium, etc.

 

What are Compounds?

A compound is a pure substance that is formed by the chemical combination of two or more elements in a fixed proportion by mass. Compound formation always takes place as a result of a chemical reaction. Therefore, a compound does not exhibit the properties of its constituent elements. On breaking down the compound, the smallest entity so obtained is called a molecule of the compound.

 

One molecule of a compound is represented by its chemical formula. The formula of a compound is the statement of the composition of that particular compound in which the symbols represent the elements that are present in it while the subscripts show the number of atoms of each element. A molecule is stable and has an independent existence.

 

The molecular formulae of some commonly used compounds are listed below:

 

Molecular Formulae of Some Commonly Used Compounds

 

Classification of Compounds

On the basis of the formation, compounds can be classified as ionic compounds and covalent compounds.

 

Ionic compounds are formed between a metal and a non-metal. They are also called electrovalent compounds as they involve ions. The metal atom loses electrons to form a cation, and the non-metal atom gains the electron to form an anion.

 

Examples include sodium chloride, magnesium iodide, calcium oxide, etc. 

 

Covalent compounds are formed between two non-metals. They are also called molecular compounds. They are formed as a result of the sharing of electrons between two or more non-metals.

 

Examples include water, carbon dioxide, methane, sugar, etc.

About the Chapter

Elements and compounds form the foundation of chemistry. Without these, two chemistry is far more incomplete. This basic foundation of chemistry is introduced to students in the ninth grade and as discussed briefly in chapter 2 called Is Matter around us pure? Just stop explaining in-depth about what are the types of mixtures around us and what are the things that form a mixture. As we all know that most of the matter that surrounds us is a mixture of two or more components for example minerals, soil, seawater all these are types of mixtures.

This chapter and the concept of elements and compounds are prescribed by the Central Board of Secondary Education CBSE so that students can inculcate a practice of questioning things that may appear unusual to them. The concept of elements and compounds is an extremely important concept as elements form the periodic table without which chemistry is nothing and these concepts are further studied in higher classes for example they are again discussed in brief in unit one of the NCERT book of class 11 in the chapter called some basic concepts of chemistry. This chapter mainly talks about the basic concepts that have already been taught in earlier classes for example the concept of elements and compounds.

Study with

The team has made the learning process much easier for students who may find it difficult to grasp the concept of ele
ments and compounds as the study notes provided by are written in an extremely simplified manner. As the main objective of producing these study notes is to help students get a clear knowledge of the basic foundations of chemistry so that they can excel in the exams and can easily study the complicated topics that will be taught later in the CBSE curriculum.

’s expert chemistry teachers have done extensive research and it is through their years of experience that they have accumulated these study notes that are based on the analysis of previous year question papers. Such research helps in producing quality notes for studious children who want to get a good score in the exam and want to have a strong base.

Key Concepts Needed to Understand Elements and Compounds

• What is A Mixture?

• Types of Mixtures

•  What is A Solution?

• Properties of A Solution

• Concentration of A Solution

• What is A Suspension?

• Properties of A Suspension

• What is A Colloidal Solution?

• Properties of A Colloid

• Separating the Components of A Mixture

• How Can We Separate A Mixture of Two Immiscible Liquids?

• How Can We Separate A Mixture of Salt And Ammonium Chloride?

• How Can We Separate A Mixture of Two Miscible Liquids?

• How Can We Obtain Different Gases From Air?

• How Can We Obtain Pure Copper Sulphate From An Impure Sample?

• Physical And Chemical Changes

• What Are The Types Of Pure Substances?

• Elements

• Compounds

Enthalpy is defined as the amount of internal energy and the output of a thermodynamic system’s pressure and volume. Enthalpy is an energy-like property or state function that has energy dimensions (and is thus calculated in joules or erg units). The enthalpy H is equivalent to the sum of the internal energy E and the pressure P multiplied with volume V of the system i.e., H = E + PV, respectively.

Under the law of conservation of energy, the shift in internal energy is equal to the heat transmitted to the device, minus the work performed by it. If a change in volume at constant pressure is the only work performed, the change in enthalpy is exactly equal to the heat transferred to the device. The amount of energy is called the enthalpy (or latent heat of vaporization) and is expressed in units of joules per mole when energy needs to be applied to a substance to shift its phase from a liquid to a gas.

Enthalpy Change

The name given to the amount of heat evolved or consumed in a reaction conducted at constant pressure is Enthalpy transition. The symbol of Enthalpy H is referred to as “delta H”. At constant pressure, the equation for the change in internal energy, ∆U = q + w can be written as:

∆U = qP – p∆V

Where qP represents the heat absorbed by the system at constant pressure and – p∆V is the expansion work done due to the heat absorbed by the system. The above equation can be written in the terms of initial and final states of the system which is defined below:

UF – UI = qP –p(VF – VI)

Or qP = (UF + pVF) – (UI + pVI)

Enthalpy (H) can be written as H= U + PV. Putting the value in the above equation, we obtained: 

qP = HF – HI = ∆H

Hence, change in enthalpy ∆H = qP, referred to as the heat consumed at a constant pressure by the system. At constant pressure, we can also write,

∆H = ∆U + p∆V

Some Key Points

The heat from the device is lost to the surrounding atmosphere during exothermic reactions. ∆H is negative for such reactions. During endothermic reactions, heat is absorbed from the atmosphere by the system. ∆H is positive for such reactions.

Enthalpy of Reactions: 

Energy change (U) is equal to the amount of heat produced and the work carried out. Pressure-volume work is called work performed by an expanding gas (or just PV work). For instance, consider a gas-producing reaction, such as dissolving a piece of copper in concentrated nitric acid. 

Cu(s)+ 4HNO3(aq) → Cu(NO3)2 (aq) + 2H2O(l) +  2NO2(g)

The quantity of PV work performed by multiplying the external pressure P by the volume change induced by the piston movement (almost V) is found. At constant external pressure, (here, atmospheric pressure),

W = −PΔV

The negative sign associated with PV work performed means that when the volume increases, the device loses energy. The work performed by the system is negative if the volume increases at constant pressure (V> 0), implying that a system has lost energy by performing work on its surroundings. Conversely, the work performed by the system is positive if the volume decreases (almost V<0), which implies that the environment has worked on the system, thereby increasing its energy.

The internal energy U of a system is the sum of all its components’ kinetic energy and potential energy. It is the inner energy shift that generates heat plus function. Chemists typically use a related thermodynamic quantity called enthalpy (H) to calculate the energy changes that occur in chemical reactions. Systems’ enthalpy is defined as the sum of their internal energy U plus the product of their pressure P and volume V:

H=U+PV

Since all state functions are internal energy, strain and volume, enthalpy is also a state function. We can therefore characterize a shift in enthalpy (‘H) accordingly.

ΔH=Hfinal −Hinitial

If at constant pressure (i.e. for a given P, ΔP=0) a chemical shift occurs, the change in enthalpy ( ΔH) is 

ΔH=Δ(U+PV)

=ΔU + ΔPV

=ΔU + PΔV

Substituting q+w for ΔU (First Law of Thermodynamics) and −w for PΔV we obtain    

ΔH=ΔU+PΔV

 =qp+w−w

 =qp

The p subscript is used here to emphasize that this equation is only valid for a constant pressure phase. It is observed that the shift in enthalpy, the H of the system, is equal to the heat obtained or lost at constant pressure.

ΔH=Hfinal−Hinitial

 =qp 

System in Thermodynamics

A thermodynamic system is a part of matter with a defined boundary on which we concentrate our attention. The system boundary might be fixed or flexible, and it can be real or fictitious. The 3 types of systems in Thermodynamics are-

• Isolated System – A system that is separated from its surroundings is unable to exchange both energy and mass. The cosmos is thought to be a self-contained system.

• Open System – Both mass and energy can be moved between the system and its surroundings in an open system. 

• Closed System – The transmission of energy happens across the closed system’s border, but the transfer of mass does not. 

Different Branches of Thermodynamics

Thermodynamics has 4 major branches, they are

• Classical Thermodynamics – The behaviour of matter is investigated using a macroscopic approach in Classical Thermodynamics. Individuals consider units such as temperature and pressure, which aids in the calculation of other properties and the prediction of the characteristics of the matter conducting the process.

• Statistical Thermodynamics – Every molecule is in the limelight in Statistical Thermodynamics, which means that the properties of each molecule and how they interact are taken into account to characterise the behaviour of a group of molecules.

Tips to study Thermodynamics

Thermodynamics is one of the most important chapters in chemistry as aspects of it (Carnot Engine), also appears again in Physics in later chapters.

Thermodynamics also has a lot of weightage in competitive exams like JEE, etc.  To get good marks in Thermodynamics, the fundamentals of the chapter, i.e. understanding of different types of systems and energy, etc must be crucial as it sets the base for the complex topic that builds on it. The students should start by going through the NCERT chapter once or twice and then solve all the NCERT Exercises. They can find solutions to these Exercises at ‘s official website. If the student has some doubts or needs revision of any topic of Thermodynamics, they can check out Vdantu’s Youtube Channel. Here they can find several video lectures on Thermodynamics and other topics. 

Teachers also conduct live sessions where questions and solutions are discussed to help the students who don’t have the best means to a teacher. Solving questions is really important for understanding Thermodynamics as it has many concepts which relate to formulas and conditions. Students can find the list of important questions of thermodynamics and other topics at ;’s official website. Previous year’s questions are also one of the most suggested ways to study and prepare for exams as it helps to break down the questioning pattern and help the student to explore different types of questions. 

This also helps them to create an exam-like situation that gives them a real test with time limits. They can find the papers and solutions at ‘s official website. Students should definitely utilize these FREE resources to clear their concepts and their way to get good marks. is trying to bring the best out of every child who wants to achieve something or has a zeal to do hard work. A little hard work with some guidance can help any child to achieve the sky and make their parents and teachers proud. 

The organic compound contributing to the flavours and even at times aromas in fruits and flowers are esters. Natural flavours and aromas are produced as a result of complex mixtures of many compounds, with esters being as a primary component. For example, the natural orange aroma is composed of 30 different esters which include 10 carboxylic acids, 34 alcohols, 34 aldehydes and ketones, and 36 hydrocarbons. The food industry always tries to mimic natural flavours by formulating artificial component. Even artificial flavours though are composed of multiple complex mixtures, yet they are not as complicated as their natural counterparts. For example, an artificial pineapple mixture has 7 esters, 3 carboxylic acids, and 7 essential oils (other natural extracts). In some cases, even an individual ester may have a similar smell to a natural aroma. Some examples include chocolate, honey, vanilla etc.

Structurally, an ester is an organic compound with an alkoxy (OR) group attached to the carbonyl group.

R may be Hydrogen, alkyl or aryl, while R’ may be alkyl or aryl only. 

 

Effect of Structure 

The rate of esterification of various alcohols and acids and their extent of the equilibrium reactions depends on the structure of the molecules and the nature of the functional substituents of the alcohol and the acids. In the process of making of acetate esters, the primary alcohols get esterified most rapidly and completely. So, the highest yield is achieved from methanol in the least time. The reaction rate is almost the same in the case of Ethyl, n-propyl, and n-butyl alcohols. But under similar conditions, the reaction rate is slower for secondary alcohols. However, wide variations are found among various members of the same series. For tertiary alcohols, the reaction rate is slow and the conversions are also nominal (1-10% at equilibrium).

The esterification of acids with straight chains like acetic, propionic, and butyric acids and others like phenylacetic and β-phenyl propionic acid happen quickly with isobutyl alcohol at 155°C. The rate of esterification is low for acids with branched chain acids as the branches are responsible for the greater retarding effect. But the formation of ester products from these substituted acids is higher than normal straight-chain ones. On the other hand, aromatic acids, benzoic and p-toluic have high equilibrium conversions though the reaction rate is slow. a nitrile group on an aliphatic acid inhibits the esterification rate. In the case of chloroacetic acids, increased chlorination results in decreasing velocity. Even double bonds retard the rate of esterification. It has been found that the esterification of that α,β-unsaturated acids are a bit complicated and time-consuming than their saturated analogues. The effect of triple bond in α,β position is similar to that of the double bonds. Both retards the process. 

Even if the double bond is removed as in erucic and brassidic acids, no such effect is found. In fact, conjugated double bonds in the α,β-position produce a greater retarding effect. 

The esterification of Cis-substituted unsaturated acids is way easier than their trans-isomers.

 

Synthesis of Esters 

The reaction of carboxylic acids, acid chlorides and acid anhydrides with alcohols result in the formation of esters. 

Alcohol reacts with a carboxylic acid in the presence of a mineral acid catalyst, such as sulfuric acid to result in esterification. 

Since these reactions result in an equilibrium mixture of both products and reactants, the reaction conditions must be deployed accordingly in order to produce a reasonable yield. In the starting mixture, a large excess of one of the reactants can be used or the alternate way could be the removal of one of the products by distillation as the reaction proceeds. This will shift the equilibrium to the right. 

Various other synthetic methods to manufacture esters are also there. The reaction of acid chlorides and alcohol also gives an ester and hydrochloric acid. To neutralize the resulting acid, a small amount of pyridine can be added to the reaction mixture. Alcohols reacting with acid anhydrides also yields an ester. But unlike the reaction involving carboxylic acid, these two reactions don’t give an equilibrium mixture.

 

I. Acid-Catalysed Esterification of a Carboxylic Acid and an Alcohol

The reaction of carboxylic acids and alcohols in the presence of an acid catalyst produces esters. Typically, strong inorganic (mineral) acid such as H₂SO₄, HCl and H₃PO₄ are used in a catalytic amount. Strong organic acids such as benzenesulphonic or p-toluenesulphonic acid are actually better preferred as they are soluble in the typical organic solvents used in organic reactions and on top of that, they can be used as catalyst without introducing any additional amount of water in the reaction equilibrium.

 

II. Acid-Catalysed Esterification of a Carboxylic Acid and an Alcohol in Excess

Methyl salicylate, the major component in the oil of wintergreen is produced by many plants of the wintergreen family. Methyl salicylate can be used as a flavouring agent (responsible for the mint flavour in chewing gum) or a fragrance. It is also a component in liniments (rubbing ointments).

 

III. Esters produced from an Acid Chloride and an Alcohol

The reaction between acid chlorides and alcohols in the presence of a weak base such as pyridine or Na₂CO₃ results in the formation of esters. The weak base manages to trap or neutralize the HCl formed in the course of the reaction. The reaction mechanism is shown as follows 

 

IV. Esterification using an Acid Anhydride and an Alcohol or a Phenol

Acid anhydrides undergo nucleophilic acyl substitution reaction with alcohols to yield esters. In the reaction, either a strong acid (H₂SO₄) or a weak base (pyridine) can be used as a strong catalyst or it may be effected by heating.

Acetylsalicylic acid, or aspirin, is one of the most widely used and versatile drugs in today’s pharma world. Charles von Gerhardt was the first one to synthesize it in 1853 and was later patented by a German dye chemist named Friedrich Bayer in 1893. The later one identified its potential as an analgesic (pain reliever). 

Salicylic acid is a component of willow and poplar bark. This had been used as a pain killer for centuries, but due to its highly acidic property, it caused irritation of the mucous membranes of the mouth and throat and even resulted in uncomfortable gastric pain. By transformation of the acidic phenol functionality into an ester group, the compound can retain its analgesic properties but have lost some of its irritating side effects. Apart from acting as a pain reliever, aspirin acts also as an antipyretic (fever reducer) and an anti-inflammatory agent (used for arthritis). But if taken in large quantities (several grams per day), it may result in gastric problems. Its use has been used in Reyes syndrome, a brain disorder affects people under the age of 18. 

Some people may be highly allergic to aspirin as well. The aspirin interferes with platelets affecting normal blood clotting that leads to haemorrhage in extreme cases. However, its anticoagulant properties make it ideal for preventing blood clots in the arteries. As per the recent studies, the consumption of one-half of an aspirin tablet per day can help the prevention of heart attacks and strokes. If acetic anhydride is used as a reactant, instead of acetic acid, it will result in rapid and irreversible conversion of salicylic acid to acetylsalicylic acid.

 

V. Reaction Mechanism of Aspirin Synthesis in the presence of Acid Catalyst

 

VI. Reaction Mechanism of Aspirin Synthesis in Neutral Media

 

Reaction of Esters 

As compared to acid chlorides, the reactivity of the esters are less.

 

Reaction Sites on a Carboxylic Group on Esters

The nucleophilic acyl substitution reaction is the most common reaction where esters react with a nucleophile. 

 

I. Hydrolysis of Esters in Basic Media

Unlike the acid chlorides that gets hydrolysed readily in water, esters do not undergo hydrolysis readily in water. The hydrolysis of esters can occur only in the presence of an acid or base catalyst. The products of the hydrolysis vary depending on whether the reaction is conducted in a basic media or an acidic media.

Hydrolysis of esters in basic media results in the formation of a carboxylate salt and alcohol, which on acidification produces a carboxylic acid and an alcohol.

 

Mechanism of Hydrolysis of Esters in Basic Media

Although hydrolysis is the breaking down by water, in a basic environment, the salt of water (NaOH or KOH) acts as a stronger nucleophile than that of the water molecule itself. Thus the former is the effective nucleophile in this alkaline or basic media.

For historical reasons, the hydrolysis of ester in aqueous hydroxide (KOH or NaOH) is known as saponification because it was used in the manufacture of soap by reacting oils or fats like triesters or triglycerides with lye that contains mainly KOH.

 

II. The reaction of Esters with Ammonia and Amines

Ester undergoes a nucleophilic substitution reaction with ammonia and amines. The substitution happens at carbonyl carbon to produce amides. The nucleophilic nature of amines and ammonia is stronger than that of water and alcohols. Even the presence of water and alcohol can help proceed with the reaction. 

 

Hydroxamate for Esters 

Just like other amines are more nucleophilic than alcohols and therefore displaces alcohols from esters, hydroxylamine is no different. It also undergoes the same mechanisms to provide hydroxamic acids. Hydroxamic acids result in highly coloured complexes that are reddish blue/ magenta in colours in ferric chloride solutions.

Learn the Properties and Use of Europium Here Easily

There are excellent elements discovered and included in the periodic table. This table comprises simple and complex divisions of elements based on their unique physical and chemical properties. One of the interesting elements we can learn from the modern periodic table is Europium. This element was discovered by Eugène-Anatole Demarçay in the year 1901. The atomic mass of this element is 151.964 AMU. On this page, you will find detailed information related to this element for easy studying and grabbing the concept. Students find themselves in a real fix when the elements are not properly described or mentioned in the textbooks. This is why the experts of have prepared this concept page where the students will be able to find the properties of Europium in a consolidated way. It will become a lot easier to study and revise the chapter when you refer to this page. Your study schedule will become extremely flexible. Let us study what is Europium and then proceed to the deeper concepts.

What is Europium?

Europium is a heavy element falling in the lanthanide group. It has a silvery shine and is metal by nature. It is the heaviest in the lanthanide group and is the most reactive element among the lanthanides. On this concept page, you will find a proper explanation of the structural, physical, and chemical properties of this element. The Europium symbol is ‘Eu’.

The Europium electron configuration is Xe 4f7 6s2. Here ‘Xe’ stands for Xenon. It is the nearest noble gas that precedes Europium. If you learn the electronic configuration of the elements using the noble gas as a parameter, it will be easier to remember the lanthanides. Let us proceed to the chemical properties of this element. The best source of this element is bastnasite and monazite.

Chemical Properties of Europium

Europium falls in the lanthanide group. It is a period 6 Block f element. As we have mentioned the atomic number before, we can easily find out that it has two valence electrons in the last orbital. It is a solid element at room temperature. The Europium melting point is 1512°F, 822°C, or 1095 K. The boiling point of this element is 2784°F, 1529°C, or 1802 K.

The atomic mass of Europium is 151.964. it has an isotope. We can define it as 153Eu. This metal is considered to be highly reactive. When exposed to air, it quickly gets tarnished after reacting with oxygen. This metal is not radioactive and is safe for plants and animals. You will be excited to know that this element is used to print Euro notes. The symbol of Europium is ‘Eu’. Its symbol is also designed following the European Union Flag and the monetary symbols.

Being the most reactive among the lanthanide, it drastically reacts with water and releases hydrogen. It forms the oxide by reacting with oxygen in the water molecules replacing hydrogen. When dipped in water, this element catches fire very quickly and reacts vigorously. Two isotopes are existing in nature, 151Eu and 153Eu.

Where Europium is Used?

Now that we have studied a small part of the metal’s physical and chemical properties, let us proceed to the uses of Europium.

• Due to the Europium mass number, it can easily absorb neutrons without causing any radioactive reaction. This is the reason why it is used as a control rod in a nuclear reactor.  

• It was found in the television tubes as Europium phosphors produce a red colour. It is also used as the activator of yttrium phosphors.

• The powerful lights used in the streets comprise a small amount of Europium. This element is also present in the mercury vapour lamps for delivering natural light.

• Europium salt is also used in paints and phosphorescence powders.

• Europium is also used for doping plastic films used in laser materials. It is also used for manufacturing superconductor alloys.

• Europium element, as mentioned earlier, is also used in printing Euro currencies to stop forgery. This anti-forgery measure stops the miscreants from copying the features of the currency across the world.

Why Prefer Using the Concept Page of ?

The experts of have scripted this concept page so that the students can easily understand what kind of element Europium is. You will be able to learn how the element behaves and what its physical and chemical properties are. Study this element using this concept page as a reference. Learn more about the Europium atomic mass and its uses using this organized material to answer the questions perfectly.