Fundamentals of Electrochemistry (original) (raw)
1 1. TABLE 1 shows the standard electrode potentials for various metals. TABLE 1 Metal ion|Metal B + |B C 2+ |C D 2+ |D E 2+ |E F 3+ |F E o (V) +0.80-0.28 +0.34-0.76 +1.42 i. Arrange the strength of the above metal ions as reducing agent in ascending order. ii. Referring to the cell notation below, write the redox equation for the cell reaction. C(s) | C 2+ (aq) || D 2+ (aq) | D(s) iii. Calculate E cell at 25 o C, if the concentrations of C 2+ and D 2+ are 0.01 M and 0.10 M respectively. [5 marks] 2. a) Explain the term standard reduction potential of hydrogen electrode and standard reduction potential of electrode. [4 marks] b) Draw a labeled diagram to show how the potential of a galvanic cell derived from the following two half reactions can be measured. Cu 2+ (aq) + 2e Cu(s) Ag + (aq) + e Ag(s) E o = 0.34 V E o = 0.80 V Explain the chemical reactions taking place in the cell. [7 marks] c) Compare and contrast between an electrolytic cell and a galvanic cell. [4 marks] 3. a) When 0.60 A of an electrical current is passed for 11.7 minutes, all the permanganate ions in 15.0 mL solution have been reduced. Determine the original concentration of permanganate ions. Given: MnO 4-+ 8H + + 5e- Mn 2+ + 4H 2 O [5 marks] b) The cell potential for the galvanic cell below is 2.299 V at 25 o C. Zn(s) | Zn 2+ (0.040 M) || Cl 2 (g, 1 atm) | Cl-(0.005 M) | Pt(s) Write the half-reactions of the anode and cathode, and the overall reaction. Calculate the standard electrode potential, E o for the Cl 2 | Cl-electrode. Determine the equilibrium constant of the reaction. (E o Zn Zn | 2 =-0.763 V) [10 marks]
Class XII Chapter 3 – Electrochemistry Chemistry
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 The following is the order in which the given metals displace each other from the solution of their salts. Given the standard electrode potentials, K + /K = −2.93V, Ag + /Ag = 0.80V, Hg 2+ /Hg = 0.79V Mg 2+ /Mg = −2.37 V, Cr 3+ /Cr = − 0.74V Arrange these metals in their increasing order of reducing power. Answer The lower the reduction potential, the higher is the reducing power. The given standard electrode potentials increase in the order of K + /K < Mg 2+ /Mg < Cr 3+ /Cr < Hg 2+ /Hg < Ag + /Ag. Hence, the reducing power of the given metals increases in the following order: Ag < Hg < Cr < Mg < K Question 3.3: Depict the galvanic cell in which the reaction Zn(s) + 2Ag + (aq) → Zn 2+ (aq) + 2Ag(s) takes place. Further show: (i) Which of the electrode is negatively charged? (ii) The carriers of the current in the cell. (iii) Individual reaction at each electrode. Answer The galvanic cell in which the given reaction takes place is depicted as: (i) Zn electrode (anode) is negatively charged.
ACS Omega
The relationship among the standard reaction Gibbs free energy ΔG°, the standard reduction potential E°, and the atomic structure parameters of radius, nuclear charge, and isoelectronic orbitals nl is accomplished through the attraction electric force F elec. In relationship with E°, it was necessary to define two new reference scales: E 0°w ith a final state of E°in the element, which allowed to have a parabolic trend of ΔG°versus F elec , and E°, 0 whose final state is the ion with a more negative charge (e.g., −1, −2, −3). The relationship with ΔG°is related to the concept of chemical stability, and the relationship with E°, 0 is more related to the concept of electronegativity. In relationship with ΔG°, it was necessary to predict the values of possible new cations and noncommon cations in order to find a better trend of ΔG°versus F elec , whose stability is analyzed by Frost diagrams of the isoelectronic series. This dependence of ΔG°on F elec is split into two terms. The first term indicates the behavior of the minimum of ΔG°for each isoelectronic orbital nl, while the second term deals with the parabolic trend of this orbital. For the minima of the configuration np 6 , a hysteresis behavior of the minima of ΔG°is found: an exponential behavior from periods 1 and 2 and a sigmoidal behavior from periods 5 and 4 to interpolate period 3. It is also found that the proximity of unfilled np or (n + 1)s orbitals induces instability of the ion in configurations ns 2 /nd 2 /4f 2 and nd 10 /nd 8 (n + 1)s 2 , respectively. On the contrary, the stability of the orbitals np 6 does not depend on the neighboring empty (n + 1)s 0 orbitals. Both phenomena can be explained by the stability of the configuration of noble gas np 6 and the nd 10 (n + 1)s 2 configuration. We have also found that it is possible to increase the reduction potential E°, 0 (macroscopic electronegativity), although the electric force F elec decreases because the orbital overlap influences the electronegativity.
Russian Journal of Electrochemistry, 2021
The relationship among the standard reaction Gibbs free energy ΔG°, the standard reduction potential E°, and the atomic structure parameters of radius, nuclear charge, and isoelectronic orbitals nl is accomplished through the attraction electric force F elec. In relationship with E°, it was necessary to define two new reference scales: E 0°w ith a final state of E°in the element, which allowed to have a parabolic trend of ΔG°versus F elec , and E°, 0 whose final state is the ion with a more negative charge (e.g., −1, −2, −3). The relationship with ΔG°is related to the concept of chemical stability, and the relationship with E°, 0 is more related to the concept of electronegativity. In relationship with ΔG°, it was necessary to predict the values of possible new cations and noncommon cations in order to find a better trend of ΔG°versus F elec , whose stability is analyzed by Frost diagrams of the isoelectronic series. This dependence of ΔG°on F elec is split into two terms. The first term indicates the behavior of the minimum of ΔG°for each isoelectronic orbital nl, while the second term deals with the parabolic trend of this orbital. For the minima of the configuration np 6 , a hysteresis behavior of the minima of ΔG°is found: an exponential behavior from periods 1 and 2 and a sigmoidal behavior from periods 5 and 4 to interpolate period 3. It is also found that the proximity of unfilled np or (n + 1)s orbitals induces instability of the ion in configurations ns 2 /nd 2 /4f 2 and nd 10 /nd 8 (n + 1)s 2 , respectively. On the contrary, the stability of the orbitals np 6 does not depend on the neighboring empty (n + 1)s 0 orbitals. Both phenomena can be explained by the stability of the configuration of noble gas np 6 and the nd 10 (n + 1)s 2 configuration. We have also found that it is possible to increase the reduction potential E°, 0 (macroscopic electronegativity), although the electric force F elec decreases because the orbital overlap influences the electronegativity.