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Questions and Answers
In a redox reaction, if a species is reduced, what occurs in terms of electron transfer and what happens to its oxidation number?
In a redox reaction, if a species is reduced, what occurs in terms of electron transfer and what happens to its oxidation number?
- It loses electrons, and the oxidation number decreases.
- It gains electrons, and the oxidation number decreases. (correct)
- It loses electrons, and the oxidation number increases.
- It gains electrons, and the oxidation number increases.
Consider the polyatomic ion $SO_4^{2-}$. What is the overall oxidation number of this ion, and what principle dictates this value?
Consider the polyatomic ion $SO_4^{2-}$. What is the overall oxidation number of this ion, and what principle dictates this value?
- -8, which is the total oxidation number of the four oxygen atoms.
- -2, because the overall oxidation number of a polyatomic ion equals its charge. (correct)
- +2, because the sum of oxidation numbers of oxygen must be positive.
- 0, because the sum of oxidation numbers in a polyatomic ion is always zero.
During a redox reaction, a substance undergoes oxidation. Which of the following statements accurately describes what happens to this substance?
During a redox reaction, a substance undergoes oxidation. Which of the following statements accurately describes what happens to this substance?
- It gains electrons and its oxidation number decreases.
- It loses electrons and its oxidation number increases. (correct)
- It gains protons and its oxidation number remains constant.
- It donates protons and its oxidation number decreases.
When balancing redox half-equations, why is it crucial to balance the oxygen atoms by adding $H_2O$ to the appropriate side of the equation?
When balancing redox half-equations, why is it crucial to balance the oxygen atoms by adding $H_2O$ to the appropriate side of the equation?
In the compound $OF_2$, what is the oxidation number of oxygen, and why does it differ from its usual oxidation number?
In the compound $OF_2$, what is the oxidation number of oxygen, and why does it differ from its usual oxidation number?
What is the primary reason for balancing redox equations, beyond simply ensuring the same number of atoms of each element on both sides?
What is the primary reason for balancing redox equations, beyond simply ensuring the same number of atoms of each element on both sides?
Consider a redox reaction where a metal atom, M, is oxidized to $M^{2+}$. What specific changes occur at the atomic level during this oxidation process?
Consider a redox reaction where a metal atom, M, is oxidized to $M^{2+}$. What specific changes occur at the atomic level during this oxidation process?
If a species is described as being reduced in a redox reaction, what directly measurable effect does it have on another species involved in the same reaction?
If a species is described as being reduced in a redox reaction, what directly measurable effect does it have on another species involved in the same reaction?
For a compound such as $H_2O$, how do you confirm that the sum of the oxidation numbers of all atoms equals zero, and what does this principle indicate about charge distribution?
For a compound such as $H_2O$, how do you confirm that the sum of the oxidation numbers of all atoms equals zero, and what does this principle indicate about charge distribution?
What is the critical role of balancing 'charge with e-' in the final step of balancing redox half-equations, and what chemical reality does it ensure?
What is the critical role of balancing 'charge with e-' in the final step of balancing redox half-equations, and what chemical reality does it ensure?
In balancing redox reactions, why is it necessary to balance hydrogen atoms ($H$) by adding $H^+$ ions, and what specific conditions does this assumption typically imply about the reaction environment?
In balancing redox reactions, why is it necessary to balance hydrogen atoms ($H$) by adding $H^+$ ions, and what specific conditions does this assumption typically imply about the reaction environment?
In an electrolytic process, if a metal ion $M^{3+}$ gains three electrons to deposit as a solid metal on the cathode, how does this reduction affect the local electrochemical environment?
In an electrolytic process, if a metal ion $M^{3+}$ gains three electrons to deposit as a solid metal on the cathode, how does this reduction affect the local electrochemical environment?
Consider a scenario where hydrogen is bonded to a metal, such as in sodium hydride ($NaH$). How does this affect the oxidation number of hydrogen, and why?
Consider a scenario where hydrogen is bonded to a metal, such as in sodium hydride ($NaH$). How does this affect the oxidation number of hydrogen, and why?
Given the unbalanced redox reaction: $MnO_4^- + Fe^{2+}
ightarrow Mn^{2+} + Fe^{3+}$ in an acidic solution, what is the stoichiometric coefficient for $Fe^{2+}$ once the equation is fully balanced?
Given the unbalanced redox reaction: $MnO_4^- + Fe^{2+} ightarrow Mn^{2+} + Fe^{3+}$ in an acidic solution, what is the stoichiometric coefficient for $Fe^{2+}$ once the equation is fully balanced?
If chlorine gas ($Cl_2$) is bubbled into a solution containing bromide ions ($Br^−$), what observable change would indicate a redox reaction has occurred, and what is the underlying chemical process?
If chlorine gas ($Cl_2$) is bubbled into a solution containing bromide ions ($Br^−$), what observable change would indicate a redox reaction has occurred, and what is the underlying chemical process?
In the context of oxidation numbers, how does the concept of electronegativity govern the assignment of oxidation states in covalent compounds?
In the context of oxidation numbers, how does the concept of electronegativity govern the assignment of oxidation states in covalent compounds?
What is the implication of the statement 'the species with the e- is getting oxidized' in terms of electron availability during a chemical reaction?
What is the implication of the statement 'the species with the e- is getting oxidized' in terms of electron availability during a chemical reaction?
Given a voltaic cell constructed with zinc and copper electrodes, predict what occurs at the zinc electrode as the voltaic cell discharges, and justify your prediction based on redox principles.
Given a voltaic cell constructed with zinc and copper electrodes, predict what occurs at the zinc electrode as the voltaic cell discharges, and justify your prediction based on redox principles.
Consider a galvanic cell where the half-reactions involve complex ion formation. How does the formation of a stable complex ion affect the reduction potential of a metal ion in the half-cell?
Consider a galvanic cell where the half-reactions involve complex ion formation. How does the formation of a stable complex ion affect the reduction potential of a metal ion in the half-cell?
Flashcards
Oxidation
Oxidation
Loss of electrons during a reaction.
Reduction
Reduction
Gain of electrons during a reaction.
Oxidation Number
Oxidation Number
The charge an atom would have if all bonds were ionic.
Oxidation number of elements
Oxidation number of elements
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Oxidation number of monatomic ions
Oxidation number of monatomic ions
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Oxidation number of Hydrogen
Oxidation number of Hydrogen
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Oxidation number of Oxygen
Oxidation number of Oxygen
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Oxidation number for polyatomic molecules
Oxidation number for polyatomic molecules
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Oxidation number in a polyatomic ion
Oxidation number in a polyatomic ion
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Balancing Redox Half Equations
Balancing Redox Half Equations
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Identifying oxidized species
Identifying oxidized species
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Identifying reduced species
Identifying reduced species
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Study Notes
Redox Reactions
- Oxidation involves gaining oxygen, losing hydrogen ions, losing electrons, and an increasing oxidation number.
- Reduction involves losing oxygen, gaining hydrogen ions, gaining electrons, and a decreasing oxidation number.
- "OIL RIG" is a mnemonic: Oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
Oxidation Number
- All elements have an oxidation number of 0 (e.g., Na, H2, N2).
- The oxidation number of monoatomic ions equals the charge of the ion (e.g., Li+, Mg2+, O2-).
- Hydrogen has an oxidation number of +1, but is -1 when joined to a metal.
- Oxygen has an oxidation number of -2, unless attached to a more electronegative atom.
- The oxidation number for a polyatomic molecule is 0 (e.g., SO3, H2SO4, C2H5OH).
- The oxidation number in a polyatomic ion equals the charge on the ion.
Balancing Redox Half Equations
- Determine formulas of all species.
- Balance all species.
- Balance oxygen atoms by adding Hâ‚‚O.
- Balance hydrogen atoms by adding H+.
- Balance charge by adding e-.
Oxidation Number Examples
- For MnO4-1:
- Oxidation number of O4 = (-2 x 4) = -8
- Mn + (-8) = -1
- Mn = +7
- For Cr2O72-:
- Oxidation number of O7 = (-2 x 7) = -14
- Cr2 + (-14) = -2
- Cr2 = +12
- Cr = +6
Electron Transfer Rule
- The species gaining electrons is getting oxidized.
- The species losing electrons is getting reduced.
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