Question 1

What is the change in the oxidation number of chromium in the following? K2Cr2O7 s Cr2(SO4)3

Accepted Answer

A) increase by three units 
B) increase by four units 
C) decrease by two units 
D) decrease by three units 
E) decrease by four units 
A) increase by three units 
B) increase by four units 
C) decrease by two units 
D) decrease by three units 
E) decrease by four units

Question 2

Which element would be the least likely to react, if at all, with water?

Accepted Answer

A) Ca 
B) Al 
C) Cu 
D) Na 
E) Zn 
A) Ca 
B) Al 
C) Cu 
D) Na 
E) Zn

Question 3

The amount of iron in a sample can be determined by a titration using dichromate ion, Cr2O72-, in acidic solution. The iron is first converted to Fe2+, which is then titrated by the dichromate ion. The reaction is:
6 Fe2+(aq)+ Cr2O72-(aq)+ 14 H+ $\rarr$ 6 Fe3+(aq)+ 2 Cr3+(aq)+ 7 H2O How many grams of iron are present in a sample if it required 42.7 mL of 0.0180 M Na2Cr2O7(aq)solution for the titration described by the redox equation above?

Accepted Answer

A) 0.043 g 
B) 0.258 g 
C) 3.61 g 
D) 7.07 g 
E) 7.15 g 
A) 0.043 g 
B) 0.258 g 
C) 3.61 g 
D) 7.07 g 
E) 7.15 g

Question 4

Consider the unbalanced redox equation, VO43-(aq)+ SO2(g)+ 2 H+(aq)$\rarr$ VO2+(aq)+ SO42-(aq)+ H2O(l)The reducing agent is

Accepted Answer

A) VO43-(aq). 
B) VO2+(aq). 
C) H+(aq). 
D) SO2(g). 
E) SO42-(aq). 
A) VO43-(aq). 
B) VO2+(aq). 
C) H+(aq). 
D) SO2(g). 
E) SO42-(aq).

Question 5

The activity series of metals is Au < Ag < Cu < Sn < Cd < Zn < Al < Mg < Na < Cs Based on this list, which element below would react most readily with a 0.10 M aqueous solution of hydrofluoric acid?

Accepted Answer

A) Ag 
B) Sn 
C) Cu 
D) Cd 
E) Zn 
A) Ag 
B) Sn 
C) Cu 
D) Cd 
E) Zn

Question 6

When a metal displaces hydrogen from a nonoxidizing strong acid, which substance is the oxidizing agent?

Accepted Answer

the H⁺ ion

Question 7

When a metal displaces hydrogen from a nonoxidizing strong acid, which substance is the reducing agent?

Accepted Answer

The answer of When a metal displaces hydrogen from a...

Question 8

What is the change in the oxidation number of nitrogen in the following? 
HNO3 $\rarr$ NO

Accepted Answer

A) increase by three units 
B) increase by four units 
C) decrease by two units 
D) decrease by three units 
E) decrease by four units 
A) increase by three units 
B) increase by four units 
C) decrease by two units 
D) decrease by three units 
E) decrease by four units

Question 9

Complete the balancing of the following half-reaction, taking place in basic media. How many hydroxide ions are needed to balance the half-reaction? Cr(OH)4(aq)$\rarr$ CrO42(aq)Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

Accepted Answer

A) 1 hydroxide ion, on the left side 
B) 3 hydroxide ions, on the right side 
C) 3 hydroxide ions, on the left side 
D) 4 hydroxide ions, on the left side 
E) 4 hydroxide ions, on the right side 
A) 1 hydroxide ion, on the left side 
B) 3 hydroxide ions, on the right side 
C) 3 hydroxide ions, on the left side 
D) 4 hydroxide ions, on the left side 
E) 4 hydroxide ions, on the right side

Question 10

Balance the half-reaction, C8H10 $\rarr$ C8H4O42, taking place in basic media. How many electrons are needed to balance the half-reaction?Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

Accepted Answer

A) 4 electrons, left side 
B) 8 electrons, right side 
C) 8 electrons, left side 
D) 12 electrons, left side 
E) 12 electrons, right side 
A) 4 electrons, left side 
B) 8 electrons, right side 
C) 8 electrons, left side 
D) 12 electrons, left side 
E) 12 electrons, right side

Question 11

When hydrocarbon compounds undergo combustion, the hydrogen is always converted into water.

Accepted Answer

A) True 
 B)False

Question 12

When hydrocarbon compounds undergo combustion, the carbon is always converted into carbon dioxide.

Accepted Answer

A) True 
 B)False

Question 13

The activity series of metals is Au < Ag < Cu < Sn < Cd < Zn < Al < Mg < Na < Cs Based on this list, which element below would undergo oxidation most readily?

Accepted Answer

A) Mg 
B) Al 
C) Cu 
D) Cd 
E) Zn 
A) Mg 
B) Al 
C) Cu 
D) Cd 
E) Zn

Question 14

Consider the redox equation below: C4H10(g)+ Cr2O72(aq)+ H+(aq)$\rarr$ H6C4O4(aq)+ Cr3+(aq)+ H2O(l)The reducing agent is

Accepted Answer

A) C4H10(g) 
B) Cr2O72(aq) 
C) H+(aq) 
D) H6C4O4(aq) 
E) Cr3+(aq) 
A) C4H10(g) 
B) Cr2O72(aq) 
C) H+(aq) 
D) H6C4O4(aq) 
E) Cr3+(aq)

Question 15

Is the following, C2O42 → CO32, an oxidation or a reduction half-reaction?

Accepted Answer

Question 16

Consider the redox equation,
2VO43-(aq)+ SO2(g)+ 8H+(aq)$\rarr$2VO2+(aq)+ SO42-(aq)+ 4H2O(l)
Which of the following is correct?Hint: Write out the oxidation numbers for each element in the equation then compare.

Accepted Answer

A) VO43-(aq)is the oxidizing agent as the oxidation number of O decreases by 3. 
B) VO2+(aq)is the reducing agent as the oxidation number of V increases by 1, causing the oxidation number of S to increase by 1 also. 
C) H+(aq)is the reducing agent, its oxidation number increases from 1 to 2, as it must have lost one electron. 
D) VO43-(aq)is the oxidizing agent, as the oxidation number of V decreases by 1, suggesting it must have accepted an electron. 
E) SO42-(aq)is the oxidizing agent and the product formed from the reduction of SO2(g). 
A) VO43-(aq)is the oxidizing agent as the oxidation number of O decreases by 3. 
B) VO2+(aq)is the reducing agent as the oxidation number of V increases by 1, causing the oxidation number of S to increase by 1 also. 
C) H+(aq)is the reducing agent, its oxidation number increases from 1 to 2, as it must have lost one electron. 
D) VO43-(aq)is the oxidizing agent, as the oxidation number of V decreases by 1, suggesting it must have accepted an electron. 
E) SO42-(aq)is the oxidizing agent and the product formed from the reduction of SO2(g).

Question 17

Is the following, Cr2O72 → Cr3+, an oxidation or a reduction half-reaction?

Accepted Answer

Question 18

The metals of Group IA undergo reduction more readily than those in any other groups of the periodic table.

Accepted Answer

A) True 
 B)False

Question 19

Zinc metal reacts with nitric acid solution to produce aqueous zinc nitrate, ammonium nitrate (in solution), and water. The species being oxidized in this reaction is

Accepted Answer

A) HNO3(aq). 
B) NH4+(aq). 
C) Zn2+(aq). 
D) Zn(s). 
E) Zn(NO3)2(aq). 
A) HNO3(aq). 
B) NH4+(aq). 
C) Zn2+(aq). 
D) Zn(s). 
E) Zn(NO3)2(aq).

Question 20

In the equation, Cu2+ (aq)+ Al(s)$\rarr$ Cu(s)+ Al3+(aq), there is one mole of each species, hence, it is balanced.

Accepted Answer

A) True 
 B)False

Exam 6: Oxidation-Reduction Reactions

What is the change in the oxidation number of chromium in the following? K2Cr2O7 s Cr2(SO4)3

Which element would be the least likely to react, if at all, with water?

Consider the unbalanced redox equation, VO43-(aq)+ SO2(g)+ 2 H+(aq) →\rarr→ VO2+(aq)+ SO42-(aq)+ H2O(l)The reducing agent is

The activity series of metals is Au < Ag < Cu < Sn < Cd < Zn < Al < Mg < Na < Cs Based on this list, which element below would react most readily with a 0.10 M aqueous solution of hydrofluoric acid?

When a metal displaces hydrogen from a nonoxidizing strong acid, which substance is the oxidizing agent?

When a metal displaces hydrogen from a nonoxidizing strong acid, which substance is the reducing agent?

What is the change in the oxidation number of nitrogen in the following? HNO3 →\rarr→ NO

Complete the balancing of the following half-reaction, taking place in basic media. How many hydroxide ions are needed to balance the half-reaction? Cr(OH)4(aq) →\rarr→ CrO42(aq)Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

Balance the half-reaction, C8H10 →\rarr→ C8H4O42, taking place in basic media. How many electrons are needed to balance the half-reaction?Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

When hydrocarbon compounds undergo combustion, the hydrogen is always converted into water.

When hydrocarbon compounds undergo combustion, the carbon is always converted into carbon dioxide.

The activity series of metals is Au < Ag < Cu < Sn < Cd < Zn < Al < Mg < Na < Cs Based on this list, which element below would undergo oxidation most readily?

Consider the redox equation below: C4H10(g)+ Cr2O72(aq)+ H+(aq) →\rarr→ H6C4O4(aq)+ Cr3+(aq)+ H2O(l)The reducing agent is

Is the following, C2O42 → CO32, an oxidation or a reduction half-reaction?

Consider the redox equation, 2VO43-(aq)+ SO2(g)+ 8H+(aq) →\rarr→ 2VO2+(aq)+ SO42-(aq)+ 4H2O(l) Which of the following is correct?Hint: Write out the oxidation numbers for each element in the equation then compare.

Is the following, Cr2O72 → Cr3+, an oxidation or a reduction half-reaction?

The metals of Group IA undergo reduction more readily than those in any other groups of the periodic table.

Zinc metal reacts with nitric acid solution to produce aqueous zinc nitrate, ammonium nitrate (in solution), and water. The species being oxidized in this reaction is

In the equation, Cu2+ (aq)+ Al(s) →\rarr→ Cu(s)+ Al3+(aq), there is one mole of each species, hence, it is balanced.

A Very Brief History of Chemistry

Scientific Measurements

Elements, Compounds, and the Periodic Table

The Mole and Stoichiometry

Molecular View of Reactions in Aqueous Solutions

Energy and Chemical Change

The Quantum Mechanical Atom

The Basics of Chemical Bonding

Theories of Bonding and Structure

Properties of Gases

Intermolecular Attractions and the Properties of Liquids and Solids

Mixtures at the Molecular Level: Properties of Solutions

Chemical Kinetics

Chemical Equilibrium

Acids and Bases, a Molecular Look

Acid-Base Equilibria in Aqueous Solutions

Solubility and Simultaneous Equilibria

Thermodynamics

Electrochemistry

Nuclear Reactions and Their Role in Chemistry

Metal Complexes

Organic Compounds, Polymers, and Biochemicals

Filters

What is the change in the oxidation number of chromium in the following? K₂Cr₂O₇ s Cr₂(SO₄)₃

Consider the unbalanced redox equation, VO₄^3-(aq)+ SO₂(g)+ 2 H⁺(aq) $\rarr$ VO²⁺(aq)+ SO₄^2-(aq)+ H₂O(l)The reducing agent is

What is the change in the oxidation number of nitrogen in the following? HNO₃ $\rarr$ NO

Complete the balancing of the following half-reaction, taking place in basic media. How many hydroxide ions are needed to balance the half-reaction? Cr(OH)₄(aq) $\rarr$ CrO₄²(aq)Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

Balance the half-reaction, C₈H₁₀ $\rarr$ C₈H₄O₄², taking place in basic media. How many electrons are needed to balance the half-reaction?Hint: Remember the coefficients when balancing half-reactions and look carefully at the oxidation numbers.

Consider the redox equation below: C₄H₁₀(g)+ Cr₂O₇²(aq)+ H⁺(aq) $\rarr$ H₆C₄O₄(aq)+ Cr³⁺(aq)+ H₂O(l)The reducing agent is

Is the following, C₂O₄² → CO₃², an oxidation or a reduction half-reaction?

Consider the redox equation, 2VO₄^3-(aq)+ SO₂(g)+ 8H⁺(aq) $\rarr$ 2VO²⁺(aq)+ SO₄^2-(aq)+ 4H₂O(l) Which of the following is correct?Hint: Write out the oxidation numbers for each element in the equation then compare.

Is the following, Cr₂O₇² → Cr³⁺, an oxidation or a reduction half-reaction?

In the equation, Cu²⁺ (aq)+ Al(s) $\rarr$ Cu(s)+ Al³⁺(aq), there is one mole of each species, hence, it is balanced.