Chem L7
What does the algebraic sum of the oxidation numbers of the atoms in a neutral compound always equal? any whole number 0 +1 -1
0
In a dry cell battery discussed in this lesson, the sides and bottom of the casing are made of which metal? nickel zinc gold chromium
zinc
What do positive ions do in a voltaic cell? Positive ions do not move. Positive ions become negative ions. Positive ions move toward the anode. Positive ions move toward the cathode.
Positive ions move toward the cathode
What species is oxidized in the following oxidation-reduction equation? MnO₄⁻ + H₂SO³ + H⁺→ Mn²+ + HSO⁴⁻ + H₂O H O Mn S
S
Consider the following reaction: Ba(s) + F₂(g) → BaF₂. Which of the following statements is true? The barium atom is gaining electrons; therefore, it is reducing agent. The fluorine atom is losing electrons; therefore, it is oxidizing agent. XXXXThe barium atom is losing electrons; therefore, it is oxidizing agent. The fluorine atom is gaining electrons; therefore, it is oxidizing agent.
The barium atom is gaining electrons; therefore, it is reducing agent???
What takes place at the cathode: The electrode loses mass Oxidation The electrode gains mass Loss of electrons
The electrode gains mass
Which of the following is true in redox reactions? Both oxidizing and reducing agents are oxidized. The reducing agent is the substance oxidized. The oxidizing agent is the substance oxidized. The reducing agent is the substance reduced.
The reducing agent is the substance oxidized.
Redox? oxidizing agent and the reducing agent? HNO₃ + H₃PO₃ → H₃PO₄ + NO
Yes, it is redox. The oxidizing agent is HNO₃, and the reducing agent is H₃PO₃.
Redox? oxidizing agent and the reducing agent? H₃AsO₄ + Zn → AsH₃ + Zn⁺²
Yes, it is redox. The oxidizing agent is H₃AsO₄, and the reducing agent is Zn.
Redox? oxidizing agent and the reducing agent? MnO₄⁻ + SO₂ → Mn⁺² + SO₄⁻²
Yes, it is redox. The oxidizing agent is MnO₄⁻, and the reducing agent is SO₂.
Determine the oxidation number of N in NO³⁻. +6 +5 -2 +1
+5
Determine the oxidation number of P in P₂O₅. +5 +3 -2 +2
+5
Oxidation #? N in Ca(NO₃)₂
+5
Oxidation #? P in P₂O₅
+5
Determine the oxidation number of Cr in Cr₂O₇⁻². +2 +3 +6 0
+6
Determine the oxidation number of Cr in K₂CrO₄. +3 +6 +2 +1
+6
Oxidation #? S in HSO₄⁻
+6
Oxidation #? S in H₂S₂O₇
+6
Oxidation #? S in Na₂SO₄
+6
Oxidation #? Mn in KMnO₄
+7
Oxidation #? S in Al₂S₃
-2
Balance: Cr₂O₇²⁻ + I⁻ → Cr³⁺ + I₂ (in basic solution)
7H₂O + Cr₂O₇²⁻ + 6I⁻ → 2Cr³⁺ + 3I₂ + 14OH⁻
Balance: H₃AsO₄ + Zn → AsH₃ + Zn⁺²
8H⁺ + H₃AsO₄ + 4Zn → AsH₃ + 4Zn⁺² + 4H₂O
What is the most common oxidation number of hydrogen when combined with elements other than itself? -1 0 +1 -2
+1
Oxidation #? N in NO₂⁻
+3
Oxidation #? N in N₂O₃
+3
Determine the oxidation number of S in SO₂. +2 -4 -2 +4
+4
Oxidation #? C in Na₂CO₃
+4
All monatomic ions have oxidation numbers equal to what? the difference of protons and electrons the number of protons the number of electrons the difference of protons and neutrons
the difference of protons and electrons
In a voltaic cell, what is the anode? the neutral electrode the electrode at which molecules gain electrons the electrode at which molecules lose electrons the electrode at which molecules can gain or lose electrons
the electrode at which molecules lose electrons
After balancing the redox equation BrO²⁻+ OH⁻+ N₂O₄ → BrO₃⁻+H₂O + NO₂⁻, what are the coefficients, in order from left to right? 1, 2, 1, 1, 1, 2 2, 2, 1, 1, 2, 2 1, 2, 1, 1, 1, 1 1, 2, 2, 1, 1, 2
1, 2, 1, 1, 1, 2
What is the voltage of the standard automobile battery? 6 V 12 V 1.5 V 50 V
12 V
In a correctly balanced redox equation, if the oxidation reaction lost two electrons how many electrons did the reduction reaction take? No relationship exists between the two numbers. 3 1 2
2
When the following redox equation is balanced correctly in acid, what is the coefficient of the HNO₃? HNO₃ + H₃PO₃→ HPO₄ + NO 1 4 3 2
2
Balance: HNO₃ + H₃PO₃ → H₃PO₄ + NO
2HNO₃ + 3H₃PO₃ → 3H₃PO₄+ 2NO + H₂O
Balance: MnO₄⁻ + SO₂ → Mn⁺² + SO₄⁻²
2H₂O + 2MnO₄⁻ + 5SO₂ → 2Mn²⁺ + 5SO₄²⁻ + 4H⁺
When the following redox equation is correctly balanced in acid, what is the coefficient of the IO₃⁻? NO + H₅IO₆ → NO₃⁻ + IO₃⁻ 2 4 3 6
3
Balance: As₂O₃ + NO₃- → H₃AsO₄ + NO
3As₂O₃ + 4H+ + 4NO₃- + 7H₂O → 6H₃AsO₄ + 4NO
How many electrons are being exchanged in the balanced redox equation Pd + 4Ag+→ Pd₄+ + 4Ag? 3 4 2 1
4
Balance: MnO₄⁻ + SO₂ → Mn⁺² + SO4⁻² (in basic solution)
4OH⁻ + 2MnO₄⁻ + 5SO₂ → 2Mn²⁺+ + 5SO₄²⁻ + 2H₂O
In the following equation, which species is the oxidized? SiO₂(s) + 2C(s) → Si(s) + 2CO(g) C O SiO₂ Si
C
When an automobile battery is charging, which of the following occurs? Energy of motion is converted to energy as heat. Electrical energy is converted to chemical energy. XXXChemical energy is converted to electrical energy. Energy as heat is converted to energy of motion.
Chemical energy is converted to electrical energy.????
What is the oxidizing agent in the following oxidation-reduction equation? H⁺ + I⁻ + Cr₂O₇²⁻→ Cr₃+ + I² + H₂O I- Cr₂O₇²⁻ Cr₃⁺ H⁺
Cr₂O₇²⁻
Balance: MnO₄⁻ + H₂SO₃ → Mn₂+ + HSO₄⁻
H⁺ + 2MnO₄⁻ + 5H₂SO₃ → 2Mn₂+ + 5HSO₄⁻ + 3H₂O
A reducing agent Is itself oxidized Does not exist in redox reactions Is itself reduced Causes another atom to be oxidized
Is itself oxidized
What happens to the oxidation number in an anode reaction? It decreases. It increases. none of these
It does not change.?
Which of the following statements correctly describes the redox equation 4H⁺ + MnO₄⁻ + 4CO → 4CO₂ + Mn₂⁺ + 2H₂O? It is not balanced for the number of atoms or charge. It is correctly balanced. It is correctly balanced for the number of atoms but not for charge. It is correctly balanced for charge but not for the number of atoms.
It is not balanced for the number of atoms or charge.
In the reaction represented by the equation: Ni³⁺ + 3e⁻ → Ni, what happens to the species Ni? It is made disproportionate. It is reduced. It is neutralized. It is oxidized.
It is reduced.
Balance: I₂ + H₂SO₃ → I⁻ + HSO₄⁻
I₂+ H₂SO₃ + H₂O → 2I⁻ + HSO₄⁻ + 3H⁺
In cell diagram notation, which half is the site of oxidation? Neither side Both sides Right Left
Left
Redox? AgNO₃ + FeCl₃ → AgCl + Fe(NO₃)₃
No
Redox? KCl + H₂SO₄ → KHSO₄ + HCl
No
When balancing redox equations, you need to balance the charge. What would you use to balance the charge if the equation were being balanced in acid? H⁺ XXXH₂O OH⁻ none of these
OH-???
What takes place at the anode: Gain of electrons Reduction The electrode gains mass Oxidation
Oxidation
In the following equation, what is the oxidizing agent? TiCl₄(l) + O₂(g) → TiO₂(s) + 2Cl₂(g) TiO₂ O₂ Cl₂ TiCl₄
O₂
What is the purpose of the salt bridge in an electrochemical cell Balances the pH of the two solutions Acts as the pathway for electrons to travel from one electrode to the other allows ions to move between the two half-cells Is the physical barrier between the anode and the cathode
allows ions to move between the two half-cells
In a voltaic cell with electrodes made from zinc and copper, the zinc is dissolved into solution as Zn²⁺. What is the zinc electrode called? reducing electrode anode metal electrode cathode
anode
When an automobile battery is charging, chemical energy is converted to electrical energy. energy as heat is converted to energy of motion. electrical energy is converted to chemical energy. energy of motion is converted to energy as heat.
chemical energy is converted to electrical energy.
When an automobile battery is starting a car, electrical energy is converted to chemical energy. energy as heat is converted to energy of motion. energy of motion is converted to energy as heat. chemical energy is converted to electrical energy.
chemical energy is converted to electrical energy.
If the reactants in a spontaneous energy-releasing redox reaction are connected externally by a wire conductor, in what form is the energy released? heat light movement electricity
electricity
Which substances react in the standard automobile battery? iron (III) oxide, iron, and sulfuric acid zinc oxide, zinc, and sulfuric acid copper (II) oxide, copper, and sulfuric acid lead (IV) oxide, lead, and sulfuric acid
lead (IV) oxide, lead, and sulfuric acid
Where does oxidation take place in an electrochemical cell? the cathode the anode or the cathode the half cell the anode
the anode
Where does reduction take place in an electrochemical cell? the cathode the anode or the cathode the half cell the anode
the cathode
In a zinc-carbon dry cell, both electrodes are auto-oxidizing and serve as both cathodes and anodes. neither electrode can be considered a cathode or an anode. the zinc electrode is the cathode, and the carbon electrode is the anode. the zinc electrode is the anode, and the carbon electrode is the cathode.
the zinc electrode is the anode, and the carbon electrode is the cathode.
In a zinc-carbon dry cell, oxidation of the zinc electrode is the cathode, and the carbon electrode is the anode. both electrodes are auto-oxidizing and serve as both cathodes and anodes. the zinc electrode is the anode, and the carbon electrode is the cathode. neither electrode can be considered a cathode or an anode.
the zinc electrode is the cathode, and the carbon electrode is the anode.
In which system does a spontaneous redox reaction produce electrical energy? electroplating cell voltaic cell electrolytic cell half cell
voltaic cell
