Redox & Reduct. Multiple Choice IB Chemistry

A particular voltaic cell is made from magnesium and iron half-cells. The overall equation for the reaction occurring in the cell is Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s) Which statement is correct when the cell produces electricity? A. Magnesium atoms lose electrons. B. The mass of the iron electrode decreases. C. Electrons flow from the iron half-cell to the magnesium half-cell. D. Negative ions flow through the salt bridge from the magnesium half-cell to the iron half-cell.

A

A voltaic cell is made from copper and zinc half-cells. The equation for the reaction occurring in the cell is Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Which statement is correct when the cell produces electricity? A. Electrons are lost from zinc atoms. B. The mass of the copper electrode decreases. C. Electrons flow from the copper half-cell to the zinc half-cell. D. Negative ions flow through the salt bridge from the zinc half-cell to the copper half-cell.

A

A voltaic cell is made from magnesium and iron half-cells. Magnesium is a more reactive metal than iron. Which statement is correct when the cell produces electricity? A. Electrons are lost from magnesium atoms. B. The concentration of Fe2+ ions increases. C. Electrons flow from the iron half-cell to the magnesium half-cell. D. Negative ions flow through the salt bridge from the magnesium half-cell to the iron half-cell.

A

The compound [Co(NH3)5Br]SO4 is isomeric with the compound [Co(NH3)5SO4]Br. What is the oxidation state of cobalt in these compounds? [Co(NH3)5Br]SO4 [Co(NH3)5SO4]Br A. +3 +3 B. +2 +1 C. +3 +2 D. +2 +3

A

The following information is given about reactions involving the metals X, Y and Z and solutions of their sulfates. X(s) + YSO4(aq) → no reaction Z(s) + YSO4(aq) → Y(s) + ZSO4(aq) When the metals are listed in decreasing order of reactivity (most reactive first), what is the correct order? A. Z > Y > X B. X > Y > Z C. Y > X > Z D. Y > Z > X

A

What are the oxidation numbers of the elements in sulfuric acid, H2SO4? Hydrogen Sulfur Oxygen A. +1 +6 -2 B. +1 +4 -2 C. +2 +1 +4 D. +2 +6 -8

A

What happens to vanadium during the reaction VO2+(aq) → VO3-(aq)? A. It undergoes oxidation and its oxidation number changes from +4 to +5. B. It undergoes oxidation and its oxidation number changes from +2 to +4. C. It undergoes reduction and its oxidation number changes from +2 to -1. D. It undergoes reduction and its oxidation number changes from +4 to +2.

A

What happens when molten sodium chloride is electrolysed in an electrolytic cell? A. Chlorine is produced at the positive electrode. B. Sodium ions lose electrons at the negative electrode. C. Electrons flow through the liquid from the negative electrode to the positive electrode. D. Oxidation occurs at the negative electrode and reduction at the positive electrode.

A

What is the reducing agent in this reaction? Cu(s) + (aq) + 4H+(aq) → Cu2+(aq) + 2NO2(g) + 2H2O(l) A. Cu(s) B. (aq) C. Cu2+(aq) D. H+(aq)

A

Which formula represents an aldehyde? A. CH3CH2CHO B. CH3COCH3 C. CH3CH2COOH D. CH3COOCH3

A

Consider the following reaction. H2SO3(aq) + Sn4+(aq) + H2O(l) → Sn2+(aq) + HSO4-(aq) + 3H+(aq) Which statement is correct? A. H2SO3 is the reducing agent because it undergoes reduction. B. H2SO3 is the reducing agent because it undergoes oxidation. C. Sn4+ is the oxidizing agent because it undergoes oxidation. D. Sn4+ is the reducing agent because it undergoes oxidation.

B

Consider the following reaction: H2SO3(aq) + Sn4+(aq) + H2O(l) → Sn2+(aq) + HSO4-(aq) + 3H+(aq) Which statement is correct? A. H2SO3 is the reducing agent because it undergoes reduction. B. H2SO3 is the reducing agent because it undergoes oxidation. C. Sn4+ is the oxidizing agent because it undergoes oxidation. D. Sn4+ is the reducing agent because it undergoes oxidation.

B

Consider the following spontaneous reactions. Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s) Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s) Zn(s) + Fe2+(aq) → Zn2+(aq) + Fe(s) Which is the correct combination of strongest oxidizing agent and strongest reducing agent? Strongest oxidizing agent Strongest reducing agent A. Ag(s) Zn(s) B. Ag+(aq) Zn(s) C. Zn2+(aq) Ag(s) D. Zn(s) Ag+(aq)

B

What are the oxidation numbers of the elements in the compound phosphoric acid, H3PO4? Hydrogen Phosphorus Oxygen A. +1 +1 -2 B. +1 +5 -2 C. +3 +1 -4 D. +3 +5 -8

B

What happens at the positive electrode in a voltaic cell and in an electrolytic cell? Voltaic cell Electrolytic cell A. Oxidation Reduction B. Reduction Oxidation C. Oxidation Oxidation D. Reduction Reduction

B

What occurs during the electrolysis of a molten salt? A. Electricity is produced by a spontaneous redox reaction. B. Electricity is used to cause a non-spontaneous redox reaction to occur. C. Electrons flow through the molten salt. D. Electrons are removed from both ions of the molten salt.

B

What occurs during the operation of a voltaic cell based on the following reaction? Ni(s) + Pb2+(aq) → Ni2+(aq) + Pb(s) External circuit Ion movement in solution A. electrons move from Ni to Pb Pb2+(aq) move away from Pb(s) B. electrons move from Ni to Pb Pb2+(aq) move toward Pb(s) C. electrons move from Pb to Ni Ni2+(aq) move away from Ni(s) D. electrons move from Pb to Ni Ni2+(aq) move toward Ni(s)

B

Which are examples of reduction? I. Fe3+ becomes Fe2+ II. Cl- becomes Cl2 III. CrO3 becomes Cr3+ A. I and II only B. I and III only C. II and III only D. I, II and III

B

Which equation represents a redox reaction? A. KOH(aq) + HCl(aq) → KCl(aq) + H2O(l) B. Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) C. CuO(s) + 2HCl(aq) → CuCl2(aq) + H2O(l) D. ZnCO3(s) + 2HCl(aq) → ZnCl2(aq) + CO2(g) + H2O(l)

B

Which equations represent reactions that occur at room temperature? I. 2Br-(aq) + Cl2(aq) → 2Cl-(aq) + Br2(aq) II. 2Br-(aq) + I2(aq) → 2I-(aq) + Br2(aq) III. 2I-(aq) + Cl2(aq) → 2Cl-(aq) + I2(aq) A. I and II only B. I and III only C. II and III only D. I, II and III

B

What process occurs at the cathode in a voltaic cell and at the anode in an electrolytic cell? Cathode of voltaic cell Anode of Electrolytic cell A. Oxidation Reduction B. Oxidation Oxidation C. Reduction Oxidation D. Reduction Reduction

C

Which statement about the following reaction is correct? 2Br-(aq) + Cl2(aq) → Br2(aq) + 2Cl-(aq) A. Br-(aq) is reduced and gains electrons. B. Cl2(aq) is reduced and loses electrons. C. Br-(aq) is oxidized and loses electrons. D. Cl2(aq) is oxidized and gains electrons.

C

Which statement is correct? A. Spontaneous redox reactions produce electricity in an electrolytic cell. B. Electricity is used to carry out a non-spontaneous redox reaction in a voltaic cell. C. Oxidation takes place at the negative electrode in a voltaic cell and the positive electrode in an electrolytic cell. D. Oxidation takes place at the negative electrode in a voltaic cell and reduction takes place at the positive electrode in an electrolytic cell.

C

5. Which processes occur during the electrolysis of molten sodium chloride? I. Sodium and chloride ions move through the electrolyte. II. Electrons move through the external circuit. III. Oxidation takes place at the positive electrode (anode). A. I and II only B. I and III only C. II and III only D. I, II and III

D

In which change does nitrogen undergo oxidation? A. NO2 → N2O4 B. NO3- → NO2 C. N2O5→ NO3- D. NH3 → N2

D

In which change does oxidation occur? A. CH3CHO → CH3CH2OH B. CrO42-→ Cr2O72- C. SO42-→ SO32- D. NO2- → NO3-

D

Magnesium is a more reactive metal than copper. Which is the strongest oxidizing agent? A. Mg B. Mg2+ C. Cu D. Cu2+

D

The following reactions are spontaneous as written. Fe(s) + Cd2+(aq) → Fe2+(aq) + Cd(s) Cd(s) + Sn2+(aq) → Cd2+(aq) + Sn(s) Sn(s) + Pb2+(aq) → Sn2+(aq) + Pb(s) Which of the following pairs will react spontaneously? I. Sn(s) + Fe2+(aq) II. Cd(s) + Pb2+(aq) III. Fe(s) + Pb2+(aq) A. I only B. II only C. III only D. II and III only

D

The oxidation number of chromium is the same in all the following compounds except A. Cr(OH)3 B. Cr2O3 C. Cr2(SO4)3 D. CrO3

D

What happens to the Cr3+(aq) ion when it is converted to CrO42-(aq)? A. Its oxidation number decreases and it undergoes reduction. B. Its oxidation number decreases and it undergoes oxidation. C. Its oxidation number increases and it undergoes reduction. D. Its oxidation number increases and it undergoes oxidation.

D

What species are produced at the positive and negative electrodes during the electrolysis of molten sodium chloride? Positive electrode Negative electrode A. Na+(l) Cl2(g) B. Cl-(l) Na+(l) C. Na(l) Cl2(g) D. Cl2(g) Na(l)

D

Which processes occur during the electrolysis of molten sodium chloride? I. Sodium and chloride ions move through the electrolyte. II. Electrons move through the external circuit. III. Oxidation takes place at the anode. A. I and II only B. I and III only C. II and III only D. I, II and III

D

Which statement is correct about an oxidizing agent in a chemical reaction? A. It reacts with oxygen. B. It reacts with H+ ions. C. It loses electrons. D. It undergoes reduction.

D

Which statement is correct for the electrolysis of a molten salt? A. Positive ions move toward the positive electrode. B. A gas is produced at the negative electrode. C. Only electrons move in the electrolyte. D. Both positive and negative ions move toward electrodes.

D

Which statement is correct? A. Oxidation involves loss of electrons and a decrease in oxidation state. B. Oxidation involves gain of electrons and an increase in oxidation state. C. Reduction involves loss of electrons and an increase in oxidation state. D. Reduction involves gain of electrons and a decrease in oxidation state

D