Importance of Electrochemical Series

Importance of Electrochemical Series A series in which the reduction electrode potentials of various electrodes have been arranged in the increasing order (downwards) is called Electrochemical Series . The standard reduction potential of hydrogen is zero.The electrodes above hydrogen have negative reduction potential while those place below it have positive reduction potential and vice-versa. To understand the importance and application of Electrochemical series we have to study about Oxidation,Reduction and Standard Reduction Potential. What is Electrochemistry? Electrochemistry is the branch of chemistry which deals with the study of the chemical changes which occur on passing electric current into certain chemical systems and also with the generation of electricity by carrying chemical reactions which are redox reactions in nature. And Redox reactions are those reactions in which both oxidation and reduction taking place. Electronic Concept of Oxidation and Reduction According to the electronic concept, oxidation may be defined as the process in which an atom or ion loses one or more electrons. The loss of electrons is also called de-electronation. As a result, there is increase in positive valency or decrease in negative valency of the species. The species which lose electrons during oxidation are called Reducing agents. According to the electronic concept, reduction may be defined as the process in which an atom or ion gains one or more electrons. The gain of electrons is also called electronation. As a result, there is increase in negative valency or decrease in positive valency of the species. The species which gain electrons during reduction are called Oxidising agents. Electrode Potential It is the potential difference between the electrode and its ions in solution. The value of Electrode potential depends upon: (i) Nature of the metal (ii) Concentration of the ions in solution. (iii) Temperature. Types of Electrode Potential Oxidation Potential:- It is the tendency of the electrode to lose electrons and as a result it gets oxidized. Reduction Potential:- It is the tendency of the electrode to accept electrons and as a result,it gets reduced. Measurement of Standard Electrode Potential (Eo):- The standard electrode potential(electron releasing or electron accepting tendency) of an electrode in contact with its electrolyte in a half cell cannot be measured experimentally due to the following reasons:- A half cell whether oxidation or reduction half cell cannot work of its own and can work only when connected to the other half cell. The electron realeasing or accepting tendency of an electrode is only relative tendency and not absolute tendency. Thus we cannot determine the absolute standard electrode potential of an electrode.To solve the problem,a reference electrode is needed and an arbitrary electrode potential must be assigned to it.The commonly used reference electrode is standard hydrogen electrode (SHE) also called normal hydrogen electrode(NHE) and its standard electrode potential (oxidation as well as reduction) is taken as zero. We have stated that a standard hydrogen electrode acts as the reference electrode and it helps in measuring the standard electrode potential of an electrode.An electrochemical cell is set up in which the metal electrode under consideration is kept in one half cell and the standard hydrogen electrode acts as the other half cell. The potential difference developed as a result of the redox reaction is measured with the help of high resistance voltmeter(or beter by potentiometer). Since the electrode potential of the hydrogen electrode under standard conditions is taken zero, the reading of the voltmeter will therefore,give the  standard electrode potential of the electrode under consideration. The deflection of the voltmeter in the cell circuit represents the flow of current. The flow of current is towards opposite side.If it is towards the metal electrode, this means that the flow of electrons is towards the standard hydrogen electrode. Therefore, metal electrode will act as anode and standard hydrogen electrode as cathode. In case, the deflection is towards the hydrogen electrode, this means that the flow of electrons is from hydrogen electrode towards the metal electrode. In such a case, hydrogen electrode will act as anode and the metal electrode as the cathode. In General, Eo cell = Eo cathode Eoanode Where Eo cell value represents the standard reduction potential of the electrode. Electrochemical Series or EMF Series :- The standard electrode potential (Eo cell) of a large number of electrodes are determined with respect to the standard hydrogen electrode acting as a reference electrode. The standard reduction potential of hydrogen is zero. The electrodes above hydrogen have negative reduction potential while those place below it have positive reduction potential and vice-versa. They are arranged in decreasing strength of reducing agent to form a series known as Electrochemical Series. Application of Electrochemical Series:- To predict the relative oxidizing and reducing powers:- The electrochemical series helps to pick out substances that are good oxidizing agents and those which are good reducing agents.In an electrochemical series the species which are placed above hydrogen are more difficult to be reduced and their standard reduction potential values are negative. The Li : Li+ (aq) electrode has the least Eo value and therefore, it is reduced with more difficulty. Therefore, Li+ cannot accept electrons easily and so loses electrons to behave as a reducing agent. Li is the strongest reducing agent. The species which are easily reduced than hydrogen are palced below it in electrochemical series and their Eo value are positive. The F2 : 2F-(aq) electrode has the highest Eo value and therefore, F2 has the greatest tendency to get reduced,it is consequently the strongest oxidizing agent. In general, oxidizing agents have + Eo values. Higher the positive value, stronger will be the oxidizing agent and reducing agents have -Eo values, higher the negative value, stronger will be the reducing agent. For Example: Increasing order of reducing power of metal is Ag+/Ag(+0.80V) Calculation of the EMF of the Cell The following steps determine the reduction potential of the cathode and anode: Step I The two half-cell reactions are written in such a way that the reaction taking place at the left hand electrode is written as an oxidation reaction and that taking place at the right electrode is written as reduction reaction. Step II The number of electrons in the two equations are made equal by multiplying one of the equations if necessary by a suitable number. However, electrode potential values (E °) are not multiplied. Step III The electrode potentials of both the electrodes are taken to be reduction potentials and so the EMF of the cell is equal to the difference between the standard potential of the right hand side and the left hand side electrode. Eo cell = Eo R EoL Step IV If the EMF of the cell is +ve, the reaction is feasible in the given direction and the cell is correctly represented, i.e., oxidation occurs at left electrode (anode) and reduction occurs at the right electrode (cathode). If it is -ve, the cell reaction is not feasible in the given direction and the cell is wrongly represented. Thus, to get positive value for the EMF the electrodes must be reversed. To predict whether a metal will react with acids to give H2 gas:- Metals above hydrogen in Electrochemical series have great tendency for oxidation,so they displace hydrogen from acids.All metals having negative electrode potentials (negative E ° values) show greater tendency of losing electrons as compared to hydrogen. So, when such a metal is placed in an acid solution, the metal gets oxidized, and H+ (hydrogen) ions get reduced to form hydrogen gas. Thus, the metals having negative E ° values liberate hydrogen from acids. metal having negative E ° value For example, metals such as Mg (E (Mg2+ Mg) = 2.37 V), Zn (E (Zn2+ Zn) = 0.76 V), Iron (E (Fe2+ Fe) = 0.44 V) etc., can displace hydrogen from acids such as HCl and HSO4. But metals such as Copper, (E (Cu2+ Cu) = + 0.34V), silver (E (Ag+ Ag) = + 0.80V) and gold (E (Au3+ Au) = +1.42 V) cannot displace hydrogen from acids because of their positive reduction potential value. To predict the Feasibility of Redox Reaction:- From the E ° values of the two electrodes one can find out whether a given redox reaction is feasible or not. A redox reaction is feasible only if the species which has higher potential is reduced i.e., accepts the electrons and the species which has lower reduction potential is oxidized i.e., loses electrons. The electrochemical series gives the increasing order of electrode potentials (reduction) of different electrodes on moving down the table. This means that the species, which accept the electrons (reduced) must be lower in the electrochemical series as compared to the other which is to lose electrons. (oxidized). For example, From the electrochemical series E ° value of Cu = +0.34 V and that of Ag = +0.80 V since the reduction potential of Ag is more than that of Cu, this means that silver has greater tendency to get reduced in comparison to copper. Thus, the reaction  occurs more readily than the reaction The reduction potential of copper is less than that of Ag, this means that copper will be oxidized or will go into solution as ions in comparison to Ag. Thus, the reaction,  occurs more readily than Therefore, silver will be reduced and copper will be oxidized and the above reaction is not feasible. Rather the reverse reaction,  can occur. Thus a metal will displace, any other metal, which occurs below it in the electrochemical series from its salt solution. When a metal having lower E ° value is placed in a solution, containing ions of another metal having higher E ° value, then the metal having lower E ° value gets dissolved and the ions of the metal having higher E ° value get precipitated. Problems Q:- Write the half-cell reaction and the overall cell reaction for the electrochemical cell: Calculate the standard emf for the cell if standard electrode potentials (reduction) Pb2+ Pb and Zn2+ Zn electrodes are -0.126V and -0.763 V respectively. Solution Zn electrode acts as anode while Pb electrode acts as cathode and, therefore oxidation occurs at zinc electrode and reduction occurs at lead electrode. The half cell reactions are: Q:- Iodine (I2) and bromine (Br2) are added to a solution containing iodide (I-) and bromide (Br-) ions. What reaction would occur if the concentration of each species is 1 M? The electrode potentials for the reactions are: Solution Since the reduction potential of Br2 is more than that of I2, it means that bromine can be readily reduced. Therefore, I- will be oxidized to I2 and this reaction should be written as oxidation. Therefore, the following reactions will occur: Since for the feasibility of the reaction, the emf should be +ve, and to get + ve value for the cell reaction, subtract the equation representing lower value of E ° from the equation representing the higher value of E °. Q:-. What will be the spontaneous reaction between the following half-cell reactions? Calculate Ecell. Solution Since the reduction potential of reaction (ii) is more than that of reaction (i); reaction (ii) will occur as reduction. Therefore, reaction (i) should be written as oxidation. To obtain the net reaction, we multiply the reactions by appropriate coefficients so that electrons get cancelled. Ecell = Esubstance reduced Esubstance oxidized = 1.28 (- 0.74) = 2.02V To predict the spontaneity of any redox reaction:- For any spontaneous reaction (deltaG) should be negative.Since deltaG = -nFE cell Hence E cell should be positive for spontaneous reaction. E cell is the emf of the cell and is calculated from the standard redox potentials by using the reaction. E cell = Ecathode Eanode If E cell is positive, the cell reaction is spontaneous, otherwise not. To predict the Replacement tendency :- The relative ease with which the various species of metals and ions may be oxidized or reduced is indicated by the reduction potential values. The metals with lower reduction potential are not reduced easily but are easily oxidized to their ions losing electrons. These electrons would reduce the other metals having higher reduction potentials. In other words, a metal having smaller reduction potential can displace metals having larger reduction potentials from the solution of their salt.For example, copper lies above silver in the electrochemical series, therefore, if copper metal is added to AgNO3 solution, silver is displaced from the solution. In general a metal occupying higher position in the series can displace the metals lying below it from the solutions of their salts and so are more reactive in displacing the other metals. Thus, Li is the most electropositive element in solutions and fluorine is the most electronegative element. To predict the correct Metallurgical Methods :- Eo values of Cu,H2O and Al are +0.34V,-0.83V and -1.66V.It means Cu gets more easily reduced than water and water gets more easily reduced than aluminium.Hence copper can be produced by the electrolysis of aqueous copper sulphate but not aluminium.this is due to the fact that when Al3+(aq) is electrolysed,the H2O will be electrolysed but not Al3+(aq). For calculation of Equilibrium Constant :- Therefore measurement of E o enables the determination of the equilibrium constant for the electrode reaction.

Impact Of Satellite TV On Our Culture Essay

1.Satellite TV (Cable TV) channels started its journey in Bangladesh at 1992. Before that, BTV was the dominant medium for about 28 years and had the monopoly power. 2.But since the birth of the satellite channels in our country, it had a detrimental effect on the society. Gradually the Bangladeshi people are losing their Bengali norms and traditions and getting used to the foreign lifestyles. AIM 3.The aim of today’s presentation is to orient the class about the mass eff of satellite TV channels on our culture and how we can overcome this prob. Scope 4.For better understanding and easy assimilation I will discuss the lesson in fol pts: a.Intro b.What is Culture? c.Major influences of satellite TV on the cultural area of Bangladesh d.Some Statistical Data e.Interpretation f.Inference g.Negative impacts of satellite TV h.Conclusion i.Remedies and Measures that can be taken What Is Culture? 5. Every particular society has its own beliefs, ways of life, art etc. This belief, customs and tradition of a society they fol is known as culture. Bangladesh has its own culture and traditions also. The culture of Bangladesh is composite and over the centuries has assimilated influences of Hinduism, Jainism, Buddhism, Islam, and Christianity. It is manifested in various forms, including music, dance, and drama, art and craft, folklore and folktale, languages and literature, philosophy and religion, festivals and celebrations, as well as in a distinct cuisine and culinary tradition. Major influences of satellite TV on the cultural area of Bangladesh 6.The influence of technological advment is changing the present world very rapidly. Changes are taking place in all spheres of life and ultimately changing the social and cultural belief systems. Satellite TV, being one of the brainchild of this technological development, is having a definite eff on the social and cultural area of Bangladesh. 7.Labib(2001) suggests an evidence showing the influence on the women and girls in fds such as fashion and clo and fast food consumption. For Bangladesh, the significant cultural shift arises due to impact of regional channels of Satellite TV, particularly Indian channels like ZeeTV, MTV, Star Plus, Sony TV are influencing the cultural sphere of Bangladesh. Through watching these, cultural ties and values are getting threatened, specifically materials that favour divorce as a means to solve family problems or programming that includes obscenity, nudity, arousal of sexual instincts, or pre-marital sexual relations are completely destroying the cultural beliefs and values of Bangladesh. 8.Indian movie world Bollywood has a curse on the culture of Bangladesh. Renowned Bangladeshi auth and columnist Muhammad Zafor Iqbal said in his column – â€Å"Upto some years ago I could boast never having seen a hindi movie,  but now I cannot. I have to travel by bus from Sylhet to Dhaka, and they show these movies where you are a captive audience.† This clearly indicates about the current picture of how Bangladeshi people are obsessed to the Indian culture, and to what extent these foreign elements has occupied our brains. Some Statistical Data 9.A research was carried out on 40 persons in Ctg based on probability sampling on 2011 to understand the influence of satellite TV on cultural changes. 10.Most of the people think cable TV is the prime reason for the exposure to foreign culture as it is the most aval and easy means. Other means aval are internet, newspapers, magazines, social awareness, general increase in the lvl of edn. But they are not considered here. The results of the svy on preference of cable TV channels by the consumers are showed in graphical form as follows: Fig: Preference of Cable Tv Channels among 40 Responders Interpretation 11.From the above bar diagram, we can see that out of 40 persons, the most viewed TV channel is Star Plus, fol by Sony TV and then HBO. All of them are foreign TV channels with no room for our own broadcasting channels. Inference 12.Over the last 10-12 years, due to this easy exposure, there is a significant change in the dimensions of culture. Research also shows that consumers preference towards some of the aspects like fashion awareness, quality preference have increased. On the other hand, bargaining habit, attraction towards traditional songs, reading habit etc has decreased whereas in some aspects there is no change. 13.Svy carr out on other parameters also showed that the changes in the dimensions which most people think that satellite TV has strong influence upon are increase in the fashion awareness, brand preference, following foreign customs, fast food consumption, interest in foreign music/movie, and for the decrease in the social bondage and good personality traits. 14.There is moderate influence upon increase in quality preference, gender balance, and knowledge based society, and decrease in the interest in Bangla movies/music. 15.There is less influence on eating out, children’s participation in decision making, and for the decrease in religious bindings. 16.A general pattern is observed in the result. People of middle/lower middle cl are affected the most rather than upper cl people possly due to their more exposure to other media/latest technology and greater awareness about changing society. Negative Impact Of Satellite 17.Some consumers were asked about the negative impacts of satellite TV on our culture. The respondents were all almost on a common footing and admit that it certainly has some negative impacts like tendency of wearing indecent/short dresses especially by the ladies and the disturbance of study for the children. They also think there is an increase in the social crime and sexual violence. Some think that it has some influence on the attraction towards smoking/drugs by the young people. Conclusion 18.The results of the study shows that over the last 8-10 years, there is clearly a change in our traditional culture and this change is likely to continue. Though all of this change is not due to the effects of satellite TV, this is playing one of the major roles as maximum exposure to the  foreign culture is due to this media. Remedies and Measures that can be taken 19.Business in today’s market is very competitive. To operate profitably in any business, the focus must be customer oriented. Like any other business, cable TV should also provide the customers with the channels they like most and improve the quality of sound and picture. People who provide the cable broadcast have a great resp towards today’s world. Therefore, corrected effort should be made to sensitize the producers and broadcasters for improving the quality of whatever prog they produce. 20.At the same time local channels should be strengthened and should have a better content. This channels should produce and broadcast quality programs that could help to promote Bangladeshi values and traditions and improve the image of Bangladesh at an international level. REFERENCE 21. Effect of Satellite Television on the Culture of Bangladesh: The Viewers Perception by Robaka Shamsher & Mohhammad Nayeem Abdullah. European Journal of Business and Management, ISSN 2222-1905 (Paper) ISSN 2222-2839 (Online) Vol 4, No.9, 2012 22.www.merriam-webster.com/ 23.http://en.wikipedia.org/wiki/Culture_of_Bangladesh

Altered Perspectives in Trifles - 729 Words

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