Passage
The tendency of a chemical species to undergo reduction during an electrochemical reaction is indicated by the standard potential E° for the reaction. As represented generally by Reaction 1, E° measures the potential Z at which element X with oxidation number N accepts N electrons and is reduced to its elemental state.X(N) + Ne⁻ → X(0) , E° = Z voltsReaction 1In a galvanic cell, E° > 0 indicates a spontaneous reaction. Therefore, chemical species with higher positive E° values are reduced more easily than those with lower E° values.Using E° as a basis of comparison, the relative thermodynamic stabilities of different chemical species involving the same element at different oxidation states can be presented graphically using a Frost diagram. For a series of compounds containing element X, a Frost diagram plots the value of NE° for each compound against the corresponding oxidation number N of element X within the species. Frost diagrams for several species containing manganese or chlorine are shown in Figure 1.
Figure 1 Frost diagrams for manganese and chlorineOn a Frost diagram, NE° is proportional to the standard Gibbs free energy ΔG° according to the relationshipΔG° = −FNE° = −nFE°Equation 1where n is the number of moles of electrons transferred during the electrochemical process and F is the Faraday constant. Free energy considerations also show that a species is prone to disproportionation if its position on the Frost diagram lies above a line connecting the points of two adjacent species, as seen for species B in Figure 2.
Figure 2 General Frost diagram for an element forming species A, B, C, and D.The slope of a line segment joining two species on a Frost diagram is equal to the standard reduction potential for the couple. A greater slope indicates a higher corresponding reduction potential. As a result, in Figure 2, the reduction potential for B to A is lower than that for D to C.
-Formal charge and oxidation state are two different ways of accounting for electrons between atoms. Based on the Lewis structure of the ClO⁻ anion, which of the following pairs of values corresponds to the formal charge of the chlorine atom and the oxidation state of the oxygen atom, respectively?

Question

Passage
The tendency of a chemical species to undergo reduction during an electrochemical reaction is indicated by the standard potential E° for the reaction. As represented generally by Reaction 1, E° measures the potential Z at which element X with oxidation number N accepts N electrons and is reduced to its elemental state.X(N) + Ne⁻ → X(0) , E° = Z voltsReaction 1In a galvanic cell, E° > 0 indicates a spontaneous reaction. Therefore, chemical species with higher positive E° values are reduced more easily than those with lower E° values.Using E° as a basis of comparison, the relative thermodynamic stabilities of different chemical species involving the same element at different oxidation states can be presented graphically using a Frost diagram. For a series of compounds containing element X, a Frost diagram plots the value of NE° for each compound against the corresponding oxidation number N of element X within the species. Frost diagrams for several species containing manganese or chlorine are shown in Figure 1.

Figure 1 Frost diagrams for manganese and chlorineOn a Frost diagram, NE° is proportional to the standard Gibbs free energy ΔG° according to the relationshipΔG° = −FNE° = −nFE°Equation 1where n is the number of moles of electrons transferred during the electrochemical process and F is the Faraday constant. Free energy considerations also show that a species is prone to disproportionation if its position on the Frost diagram lies above a line connecting the points of two adjacent species, as seen for species B in Figure 2.

Figure 2 General Frost diagram for an element forming species A, B, C, and D.The slope of a line segment joining two species on a Frost diagram is equal to the standard reduction potential for the couple. A greater slope indicates a higher corresponding reduction potential. As a result, in Figure 2, the reduction potential for B to A is lower than that for D to C.
-Formal charge and oxidation state are two different ways of accounting for electrons between atoms. Based on the Lewis structure of the ClO⁻ anion, which of the following pairs of values corresponds to the formal charge of the chlorine atom and the oxidation state of the oxygen atom, respectively?

Quizplus · Accepted Answer

11ecba2d_1223_e656_a3bf_3d7876181ca1_MD0008_00 Formal charge and oxidation state (oxidation number) are two different methods used to account for electrons around an atom. Formal charge and oxidation state are not necessarily equal because these values signify different aspects related to chemical bonding. Formal charge assesses the allocation of charge to the atoms in a Lewis structure based on the bonding configuration of the atoms. Oxidation state assesses the gain or loss of electrons by an atom (relative to the elemental valence configuration) due to bond formation. The formal charge (FC) accounting method assumes that the electrons in a covalent bond are shared equally, and FC is calculated as: 11ecba2d_1224_0d67_a3bf_8dc5ebb30fce_MD0008_00 The oxidation state (OS) accounting method assigns all bonding electrons in a given bond to the most electronegative atom of the bond, and OS is calculated as: 11ecba2d_1224_0d68_a3bf_39a668ad54f3_MD0008_00 Applying these formulas to the Lewis structure of CIO⁻, the formal charge of the chlorine atom and the oxidation state of the oxygen atom are calculated to be 0 and −2, respectively. 11ecba2d_1224_0d69_a3bf_239e610222b8_MD0008_00 11ecba2d_1224_0d6a_a3bf_c165d15a60d1_MD0008_00 (Choice A) The values +1 and −1 are the oxidation state of chlorine and the formal charge of oxygen, respectively, rather than the formal charge of the chlorine atom and the oxidation state of the oxygen atom. (Choice B) The values 0 and −1 are the respective formal charges of the chlorine and oxygen atoms rather than the formal charge of the chlorine atom and the oxidation state of the oxygen atom. (Choice D) Although chlorine often takes an oxidation state of −1 when bound to atoms with a lower relative electronegativity, oxygen is more electronegative than chlorine and causes chlorine to take an oxidation state of +1 in ClO⁻. However, the question asks for the formal charge of the chlorine atom (not its oxidation state). Educational objective: Formal charge assesses the allocation of charge to an atom by dividing bonding electrons evenly between atoms. Oxidation state assesses the gain or loss of electrons by an atom by assigning all bonding electrons to the more electronegative atom.

Passage The Tendency of a Chemical Species to Undergo Reduction During