Answer The Following Questions That Relate To Electrochemical Reactions
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[DOWNLOAD] Answer The Following Questions That Relate To Electrochemical Reactions
Question 5. Suggest structure of these compounds. Count for the fallacy. Answer: O. By conventional method, the O. This fallacy is overcome if we calculate the O. Question 6. Question 7. Answer: Question 8. While sulphur dioxide and hydrogen...[GET] Answer The Following Questions That Relate To Electrochemical Reactions | updated!
Therefore, O in H2O2 can either decrease its O. Therefore, H2O2 acts both as an oxidising as well as a reducing agent. It can only decrease its O. Therefore, O3 acts only as an oxidant. Therefore, it can only decrease its O. Question 9. Answer: a...
NCERT Solutions For Class 11 Chemistry Chapter 8 Redox Reactions
However, in industry alcoholic KMnO4 is preferred over acidic or alkaline KMnO4 because of the following reasons: i The cost of adding an acid or the base is avoided because in the neutral medium, the base OH- ions are produced in the reaction itself. H2S04 is added to an inorganic mixture containing chloride, a pungent smelling gas HCl is produced because a stronger acid displaces a weaker acid from its salt.- However, when the mixture contains bromide ion, the initially produced HBr being a strong reducing agent than HCl reduces H2S04to S02 and is itself oxidised to produce red vapour of Br2. Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions. Answer: Question Consider the reactions: Why does the same reductant, thiosulphate react difforerently with iodine and bromine? Answer: The average O. The O. It is because of this reason that thiosulphate reacts differently with Br2 and I2. Justify-giving reactions that among halogens, fluorine is the best oxidant and among hydrohalic compounds, hydroiodic add is the best reductant.
- Answer: Halogens have a strong tendency to accept electrons. Therefore, they are strong oxidising agents. Their relative oxidising power is, however, measured in terms of their electrode potentials. Conversely, halide ions have a tendency to lose electrons and hence can act as reducing agents. Since the electrode potentials of halide ions decreases in the order: I— Thus, hydroiodic acid is the best reductant. This is supported by the following reactions. Thus, HI is a stronger reductant than HBr. Why does the following reaction occur? Balance the following redox reactions by ion-electron method. Balance the following equation in basic medium by ion electron method and oxidation number method and identify the oxidising agent and the reducing agent. Thus, cyanogen is simultaneously reduced to cyanide ion and oxidised to cyanate ion. Write a balanced ionic equation for the reaction. Answer: a F. Fluorine being the most electronegative element shows only a -ve oxidation state of Because of the presence of seven electrons in the valence shell, I shows an oxidation state of -1 in compounds of I with more electropositive elements such as H, Na, K, Ca, etc.
- Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess chlorine is removed by treating with sulphur dioxide. Present a balanced equation for the reaction for this redox change taking place in water. Answer: The skeletal equation is: Question Refer to the periodic table given in your book and now answer the following questions. What is the maximum wight of nitric oxide that can be obtained starting only with Answer: The balanced equation for the reaction is: But the amount of O2 which is actually available is Therefore, 02 is the limiting reagent and hence calculations must be based upon the amount of 02 taken and not on the amount of NH3 taken. Using the standard electrode potentials given in Table 8.
- Answer: a It may be noted that for oxidation reactions, i. To get the equation for the overall reaction, the number of electrons lost in Eq. To do so, Eq. Further, it may be noted that whenever any half reaction equation is multiplied by any integer, its electrode potential is not multiplied by that integer. Writing electrode potential for each half reaction from Table 8. Predict the products of electrolysis in each of the following: i An aqueous solution of AgNO3 with silver electrodes. Similarly, at the anode, either Ag metal of the anode or H2O molecules may be oxidised. It may, however, be mentioned here that the oxidation potential of N03—ions is even lower than that of H2O since more bonds are to broken during reduction of N03 ions than those in H2O.
- As a result, O2 is liberated at the anode according to equation iv. Similarly at the anode, either SO aq ions or H2O molecules are oxidised. Since the oxidation potential of SO4 is expected to be much lower since it involved cleavage of many bonds as compared to those in H20 than that of HjO molecules, therefore, at the anode, it is H2O molecules rather than SO ions which are oxidised to evolve O2 gas. From the above discussion, it follows that during electrolysis of an aqueous solution of H2S04 only the electrolysis of H2O occurs liberating H2 at the cathode and O2 at the anode. Similarly, at the anode, either Cl— aq ions or H2O molecules are oxidised.
- Thus, when an aqueous solution of CuCl2 is electrolysed, Cu metal is liberated at the cathode while Cl2 gas is evolved at the anode. Arrange the following metals in the order in which they displace each other from the solution of their salts. Al, Cu, Fe, Mg and Zn. Answer: It is based upon the relative positions of these metals in the activity series. Arrange these metals in increasing order of their reducing power. Answer: Lower the electrode potential, better is the reducing agent.
- Explain what is meant by 'the free energy of an electrochemical cell'. Propose a simple experiment to estimate the entropy change DS associated with an electrochemical reaction. Define the standard conditions associated with a gas? Explain why it is much easier to use molarity instead of activity to describe the presence of an ionic species. Explain your answer. Why are electrochemical cells described using typically two half cells? Define the purpose of what is called the Stockholm convention in the context of electrochemistry. SHE would be if the potential had been measured with a saturated silver chloride electrode? What does a measured potential value of SCE would be if the potential had been measured with a saturated silver chloride electrode? Propose and explain your choice of a reference electrode for measuring the corrosion potential of a piece of metal buried in soil. Propose and explain your choice of a reference electrode for measuring the corrosion potential of a piece of metal immersed in a very alkaline environment.
- What is the electrochemical principle of a pH glass electrode? What instrument would you use to measure directly the pH of a soil? Can one predict the corrosion rate of a metal in a given environment with E-pH diagrams? Can one predict which corrosion products will form on a metal in a given environment with E-pH diagrams? What would be the maximum voltage produced by such a cell running on pure hydrogen and air in an acidic environment? Would it be different if pure oxygen was used instead of ambient air? Repeat question 21 for an alkaline environment. Use the E-pH diagram for aluminum shown in Figure 4. SHE and pH values of 2, 4, 6, 8, and 10? Define the predominance domain of aluminum metallic element in terms of pH and potential. Define the predominance domain of aluminum oxide in terms of pH and potential. Would this aluminum oxide be protective on aluminum components? Please search the book to support your conclusion. Use the E-pH diagram for iron shown in Figure 4.
- Define the predominance domain of iron metallic element in terms of pH and potential. Define the predominance domain of rust or Fe OH 3 in terms of pH and potential. Would rust be protective on steel and iron? Corrosion Kinetics and Applications of Electrochemistry to Corrosion V isual aids Describe in your own words the significance of what is meant by 'overpotential'. Describe the principles of a potentiodynamic scan. Describe in your own words the significance of what is meant by the 'exchange current density' in reference to a corrosion reaction. Would steel be a good electrode material for the production of hydrogen in an electrochemical cell? Considering what has been discussed in Chapter four would you suggest that such a process would be easier on the steel in an alkaline or an acidic environment?
- What is the chemical significance of a polarization branch? Can one use direct current to measure the ohmic drop in an electrochemical cell? How can a Luggin capillary improve the polarization measurement at an electrode? Describe, in your own words, the methodology applied to estimate the ground resistivity for various soil depths. What is the role of the two central pins in the Wenner method? Describe the main advantages of each of the soil resistivity methods that have been used to measure soil resistivity.
Frank Solutions For ICSE Class 10 Chemistry Part 2 Chapter 6 - Electrolysis [Latest Edition]
Was is the purpose of graphing out an Evans diagram? How does one determine the corrosion potential from a mixed potential diagram. How does one determine the corrosion current from a mixed potential diagram. Describe the main components required to carry out some electrochemical polarization tests. Describe the main differences between potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy. Indicate what your arguments to propose one technique over another would be.- Provide some application examples of corrosion monitoring techniques, Highlighting the advantages and costs associated with these practices. Describe the selection criteria that would make the choice of anodic protection a better choice than cathodic protection. Describe two electrochemical techniques that are used in corrosion studies but not mentioned in the book. Explain their principles and main uses. Recognizing the Forms of Corrosion V isual aids Search the Internet for examples to illustrate the inspectability of the forms of corrosion listed in the three groups described in pages and Provide some examples to illustrate that statement.
- Provide some examples in support of that statement. The actual importance of a type of corrosion may greatly vary between affected systems. Provide some examples of uniform corrosion with pictures and general description. Provide examples and explanation. Provide some examples of pitting corrosion with pictures and general description. Provide, from a basic search of the Internet, some details of the nature and chemistry of tubercles in water pipes. Where might pitting undercutting be a serious design consideration? Relate metallurgical features of a metallic material to the shapes of corrosion pits shown in Figure 6. Elaborate on the three types of pitting that have been observed on copper in water service.
- Why would stray currents be such a force to reckon with behind one of the most dramatic forms of pitting corrosion experienced in service? Use Faraday's law to support your arguments. Propose a simple algorithm to estimate the pit density obtained from micrographs taken on corroded samples. What would be the main purpose for using extreme value statistics for the evaluation of field coupons.
Chapter 11 – Electron Transfer Reactions And Electrochemistry
Provide some examples of crevice corrosion different from those described in the book. Extend the crevice corrosion scenario to situations encountered with non-metallic materials. Why would it be misleading to call a galvanic corrosion process 'electrolysis', as many still refers to when discussing galvanic corrosion. Why would the order of metals in galvanic series vary with environments? Copper ions even in very low concentrations may deposit readily on an aluminum surface. First explain the deposition process itself before explaining why deposited copper nodules on the aluminum surface could lead to greatly accelerated corrosion of the aluminum material.- Explain why intergranular corrosion is often considered to be a localized form of galvanic corrosion. Dealloying is in many ways similar to galvanic corrosion. Highlight the similarities and differences between these two technically different forms of corrosion. Describe some field examples of hydrogen induced cracking and discuss some of the mechanisms that have been proposed to explain these problems. How can hydrogen blistering be avoided? Describe in simple words the main differences between laminar flow and turbulent flow in the context of velocity induced corrosion.
- Flow accelerated corrosion is a particularly serious concern in the energy industry. Find some examples and cases to support that statement. Provide some recommendations for the selection of an alloy to be used for the construction of a system handling high velocity seawater. Provide a detailed mechanism invoking the collapse of bubbles to explain damage caused by cavitation corrosion. Provide some recommendations for the selection of an alloy to be used for the construction of a system handling high levels of hydrogen sulfide in a low pH water.
- Summarize the various characteristics and impact of the different types of cavitation that have been observed. Describe the consecutive steps that may occur when a SCC problem results in a full catastrophic failure, putting a special emphasis on the time scale involved in each of these steps. Why is SCC generally described as an anodic process? Are pure metals as susceptible to SCC as their alloys. Provide some examples. Will fatigue corrosion affect metals and alloys that have usually a good endurance limit? Chapter Seven : Corrosion Failures, Factors, and Cells V isual aids Describe situations where the forms of corrosion would be a better way of looking at problems and other cases where looking at factors leading to these corrosion problems would provide a better angle. Provide some examples where each of the following factors would be of paramount importance in relation to aqueous corrosion: temperature, fluid velocity, impurities in the environment, presence of microbes, and presence of stray currents.
- Provide some examples of what is referred to as 'nominal chemistry' and 'prior chemistry history' in the context of a location for analysis matrix. Propose some useful applications of the survey results summarized in Figure 7. Provide some examples of corrosion cells other than those described in the book. Figure 7. Discuss these factors using practical examples of galvanic corrosion. Specify the scientific nature of these factors and provide an indication of the importance of the role they play. Find and discuss data related to the conductivity of the environments associated with the anchor support examples discussed in Chapter seven. Estimate the potential gradients that may develop between various sections of a submerged steel pile. Assume that these gradients are caused by dissolved oxygen and use data provided in previous Chapters to justify your assumptions.
- It also looks at how you go about choosing a suitable oxidising agent or reducing agent for a particular reaction. Important: This is the final page in a sequence of five pages about redox potentials. You will find it much easier to understand if you start from the beginning. Links at the bottom of each page will bring you back here again.
- Don't try to short-cut this. Redox potentials are absolutely simple to work with if you understand what they are about. If you don't, the whole topic can be a complete nightmare! Predicting the feasibility of a possible redox reaction A reminder of what you need to know Standard electrode potentials redox potentials are one way of measuring how easily a substance loses electrons. Remember that this is always relative to the hydrogen equilibrium - and not in absolute terms. Whenever you link two of these equilibria together either via a bit of wire, or by allowing one of the substances to give electrons directly to another one in a test tube electrons flow from one equilibrium to the other.
- That upsets the equilibria, and Le Chatelier's Principle applies. The positions of equilibrium move - and keep on moving if the electrons continue to be transferred. Note: If you aren't confident about this, please go back and start from the beginning of this sequence of pages. All these ideas are explored in a gentle and logical way. Will magnesium react with dilute sulphuric acid? Of course it does! I'm choosing this as an introductory example because everybody will know the right answer before we start.
- We have also explored this from a slightly different point of view on the previous page in this sequence. The sulphate ions are spectator ions and play no part in the reaction. Think of it like this. There is no need to write anything down unless you want to. With a small amount of practice, all you need to do is just look at the numbers. Is there anything to stop the sort of movements we have suggested? The magnesium can freely turn into magnesium ions and give electrons to the hydrogen ions producing hydrogen gas. The reaction is feasible. Now for a reaction which turns out not to be feasible. Will copper react with dilute sulphuric acid? You know that the answer is that it won't. Is this possible? If we start from copper metal, the copper equilibrium is already completely to the right.
- Similarly, if we start from hydrogen ions from the dilute acid , the hydrogen equilibrium is already as far to the left as possible. There is no possibility of a reaction. In the next couple of examples, decide for yourself whether or not the reaction is feasible before you read the text. The other one tends to move to the right. Is that possible? Yes, it is possible. Given what you are starting from, these equilibrium shifts are impossible. However, because we are starting from manganese II ions, it is already as far to the right as possible. In order to get any reaction, the equilibrium would have to move to the left. This reaction isn't feasible. Will dilute nitric acid react with copper?
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