REDOX Test

Identify the substance being oxidized in the following reaction: CH4 + 2O2 -> CO2 + 2H2O A. CH4 B. O2 C. CO2 D. H2O E. None of the above

A. CH4

What is the balanced oxidation half-reaction for the following unbalanced redox reaction: Ca(s) + Ag+(aq) -> Ca2+(aq) + Ag(s) A. Ca -> Ca2+ + 2e- B. 2Ag+ + 2e- -> 2Ag C. Ag+ -> Ag + e- D. 2e- + Ca -> Ca2+ E. none of the above

A. Ca -> Ca2+ + 2e-

A salt bridge is used to: A. allow the ion flow necessary for cell neutrality B. determine the direction of cell reaction C. provide reactants in a fuel-cell D. Control whether the cell is electrolytic or galvanic

A. allow the ion flow necessary for cell neutrality

What is the oxidation number of nitrogen in NCl3? A. -3 B. +3 C. 0 D. -5 E. -1

B. +3

What is the standard sell potential for the reaction below? Mg(s) + Br2(l) -> Mg2+(aq) + 2Br-(aq) The standard reduction potential is -2.37 V for the Mg2+/Mg half-cell and +1.09 V for the Br2/Br- half-cell. A. +1.28 V B. +3.46 V C. -1.28 V D. -3.46 V

B. +3.46 V

A galvanic cell consists of one half-cell that contains Ag(s) and Ag+(aq), and one half-cell that contains Cu(s) and Cu2+(aq). What species are produced at the electrodes under standard conditions? Ag+(aq) + e- → Ag(s) E° = +0.80 V Cu2+(aq) + 2 e- → Cu(s) E° = +0.34 V A. Ag(aq) is formed at the cathode and, Cu(s) is formed at the anode. B. Ag(s) is formed at the cathode, and Cu2+(aq) is formed at the anode. C. Cu(s) is formed at the cathode, and Ag+(aq) is formed at the anode. D. Cu2+(aq) is formed at the cathode, and Cu(s) is formed at the anode.

B. Ag(s) is formed at the cathode, and Cu2+(aq) is formed at the anode.

Which species is oxidized in the reaction: CuSO4(aq) + Fe(s) → FeSO4(aq) + Cu(s)? A. Cu(s) B. Fe(s) C. CuSO4(aq) D. FeSO4(aq)

B. Fe(s)

In which compound does manganese have the highest oxidation state? A. MnO2 B. KMnO4 C. Mn2O3 D. Mn E. None of the above

B. KMnO4

For the galvanic cell reaction, expressed below using shorthand notation, what half-reaction occurs at the anode? Mg(s) | Mg2+(aq) || Cd2+(aq) | Cd(s) A. Mg2+(aq) + 2e- -> Mg(s) B. Mg(s) -> Mg2+(aq) + 2e- C. Cd(s) -> Cd2+(aq) + 2e- D. Cd2+(aq) + 2e- -> Cd(s)

B. Mg(s) -> Mg2+(aq) + 2e-

Assign the oxidation state of each atom in sodium sulfate, Na2SO4. A. Na = +1, S = +4, O = -2 B. Na = +1, S = +6, O = -2 C. Na = +2, S = -2, O = 0 D. Na = +2, S = +6, O = -2 E. Na = +1, S = -2, O = +4

B. Na = +1, S = +6, O = -2

Which is the reduction half-reaction for the following overall cell reaction? Ni2+(aq) + 2Ag(s) -> Ni(s) + 2Ag+(aq) A. Ag+(aq) + e- -> Ag(s) B. Ni2+(aq) + 2e- -> Ni(s) C. Ni2+(aq) + e- -> Ni(s) D. Ag(s) + e- -> Ag+(aq)

B. Ni2+(aq) + 2e- -> Ni(s)

Identify the substance being reduced in the following reaction: CH4 + 2O2 -> CO2 + 2H2O A. CH4 B. O2 C. CO2 D. H2O E. None of the above

B. O2

What is the oxidation state of the underlined atom in the compound: H2SO4 (O is underlined) A. +1 B. +2 C. -2 D. +6 E. +4

C. -2

What is the oxidation number of the atoms in chlorine gas? A. -1 B. -8 C. 0 D. -7 E. -5

C. 0

For a galvanic cell that uses the following two half reactions, Cr2O7 2-(aq) + 14 H+(aq) + 6 e- → 2 Cr3+(aq) + 7 H2O(l) Pb(s) → Pb2+(aq) + 2 e- how many moles of Pb(s) are oxidized by one mole of Cr2O7 2-? A. 6 B. 2 C. 3 D. 1

C. 3

What is oxidized and what is reduced in the following reaction? 2Al + 3Br2 -> 2AlBr3 A. Al is reduced and Br2 is oxidized. B. AlBr3 is oxidized and Al is reduced. C. Al is oxidized and Br2 is reduced. D. AlBr3 is reduced and Br2 is oxidized. E. AlBr3 is reduced and Al is oxidized.

C. Al is oxidized and Br2 is reduced.

Which cell involves a non-spontaneous redox reaction? A. Galvanic cell B. Fuel cell C. Electrolytic cell D. Concentration cell

C. Electrolytic cell

Determine whether this is a galvanic or a electrolytic cell and given the reaction occurring at the anode and the reaction occurring at the cathode. A. Galvanic cell Anode reaction: K(s) -> K+(l) + e- Cathode reaction: Cl2(g) + 2e- -> 2Cl-(l) B. Electrolytic cell Anode reaction: K(s) -> K+(l) + e- Cathode reaction: Cl2(g) + 2e- -> 2Cl-(l) C. Electrolytic cell Anode reaction: 2Cl-(l) -> Cl2(g) + 2e- Cathode reaction: K+(l) + e- -> K(s) D. Galvanic cell Anode reaction: K(s) -> K+(l) + e- Cathode reaction: Cl2(g) + 2e- -> 2Cl-(l)

C. Electrolytic cell Anode reaction: 2Cl-(l) -> Cl2(g) + 2e- Cathode reaction: K+(l) + e- -> K(s)

In an electrochemical cell, which of the following statements is FALSE? A. Reduction occurs at the cathode. B. A spontaneous electrochemical cell is called a voltaic cell. C. Electrons flow through the salt bridge to complete the cell. D. Oxidation occurs at the anode. E. All of the above are true.

C. Electrons flow through the salt bridge to complete the cell.

Assign the oxidation state of each atom in potassium chlorate, KClO3. A. K = -1, Cl = +1, O = 0 B. K = -1, Cl = -1, O = +2 C. K = +1, Cl = +5, O = -2 D. K = +1, Cl = +1, O = -2 E. K = +1, Cl = -1, O = 0

C. K = +1, Cl = +5, O = -2

Which element is reduced in the reaction below? I- + MnO4- + H+ -> I2 + MnO2 + H2O A. H B. I C. Mn D. O

C. Mn

What must be done to the following half-reactions before they can be added together? Mn(s) -> Mn2+(aq) + 2e- Fe3+(aq) + 3e- -> Fe(s) A. Double the Mn half-reaction and triple the Fe half-reaction. B. Double the Mn half-reaction. C. Triple the Mn half-reaction and double the Fe half-reaction. D. Add H+ ions to the left-side of the Mn reaction. E. None of the above

C. Triple the Mn half-reaction and double the Fe half-reaction.

An electrolytic cell is: A. a battery B. a cell in which reactants are continuously supplied to the cell C. a cell in which an electric current drives a non-spontaneous reaction D. a cell in which the cell reaction is spontaneous

C. a cell in which an electric current drives a non-spontaneous reaction

What is the oxidation state of the underlined atom in the compound: CO2 (C is underlined) A. +1 B. +2 C. -2 D. +4 E. +6

D. +4

Oxidation involves which of the following? 1. Loss of electrons 2. Gain of electrons 3. Increase in oxidation state A. 2 only B. 1 only C. 3 only D. 1 and 3 only E. 2 and 3 only

D. 1 and 3 only

What is the shorthand notation that represents the following galvanic cell reaction? Fe(s) + Cu(NO3)2(aq) -> Fe(NO3)2(aq) + Cu(s) A. Cu(s) | Cu(NO3)2(aq) || Fe(NO3)2(aq) + Cu(s) B. Cu(s) | Cu2+(aq) || Fe2+(aq) | Fe(s) C. Fe(s) | NO3-(aq) || NO3-(aq) | Cu(s) D. Fe(s) | Fe2+(aq) || Cu2+(aq) | Cu(s)

D. Fe(s) | Fe2+(aq) || Cu2+(aq) | Cu(s)

Which of the following terms can be used to describe an electrochemical cell in which a spontaneous chemical reaction generates an electric current? I. an electrolytic cell II. a galvanic cell III. a voltaic cell A. Only I B. Only II C. Only III D. II and III

D. II and III

For the galvanic sell reaction, express below using shorthand notation, what half reaction occurs at the cathode? Zn(s) | Zn2+(aq) || Ni2+(aq) | Ni(s) A. Zn(s) -> Zn2+(aq) + 2e- B. Ni(s) -> Ni2+(aq) + 2e- C. Zn2+(aq) + 2e- -> Zn(s) D. Ni2+(aq) + 2e- -> Ni(s)

D. Ni2+(aq) + 2e- -> Ni(s)

In the shorthand notation for a galvanic cell, a double vertical line (||) represents: A. a phase boundary B. a double phase boundary C. an inert electrode D. a salt bridge

D. a salt bridge

Reduction typically involves: A. the gain of oxygen B. the gain of water C. the loss of electrons D. the gain of electrons E. none of the above

D. the gain of electrons

Oxidation typically involves: A. the gain of electrons B. the gain of water C. the loss of oxygen D. the loss of electrons E. none of the above

D. the loss of electrons

Reduction involves which of the following? 1. Loss of electrons 2. Gain of electrons 3. Decrease in oxidation state A. 2 only B. 3 only C. 1 only D. 1 and 2 only E. 2 and 3 only

E. 2 and 3 only

In an electrochemical cell, which of the following statements is FALSE? A. A salt bridge provides electrical contact between the half-cells B. A spontaneous electrochemical cell is called a galvanic cell C. The cathode is the electrode where reduction occurs D. The anode is the electrode where oxidation occurs E. All of the above are true.

E. All of the above are true.

In the following reaction, what substance gains electrons? 2Fe3+(aq) + Sn2+(aq) -> 2Fe2+(aq) + Sn4+(aq) A. Sn4+(aq) B. H2O(l) C. Fe2+(aq) D. Sn2+(aq) E. Fe3+(aq)

E. Fe3+(aq)

In the following reaction, what substance loses electrons? 2Fe3+(aq) + Sn2+(aq) -> 2Fe2+(aq) + Sn4+(aq) A. Fe3+(aq) B. H2O(l) C. Fe2+(aq) D.Sn4+(aq) E. Sn2+(aq)

E. Sn2+(aq)

(Image of KCl)

Electrons flows from anode to cathode; Cl- ions flow towards the anode and Cl- flows towards the cathode.

Oxidation occurs at the cathode.

False

The oxidation number of a chlorine atom is -1.

False

The oxidation number of sulfur in SO3 is -6.

False

Electrical current can be used to drive a non-spontaneous redox reaction.

True

Electrons flowing through a wire is an example of electric current.

True

Oxidation is the loss of electrons.

True

Reduction is the gain of electrons.

True

The cathode is the electrode at which reduction occurs.

True

The oxidation number of manganese in MnO4^-1 is +7.

True

The oxidation number of sodium in NaI is +1.

True