BYU Online: Chemistry 043: Speedback Lesson 8

In a dry cell battery discussed in this lesson, the sides and bottom of the casing are made of which metal? gold chromium zinc nickel

zinc

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 oxidized. The fluorine atom is gaining electrons; therefore, it is oxidized. The barium atom is losing electrons; therefore, it is oxidized. The fluorine atom is losing electrons; therefore, it is reduced.

The barium atom is losing electrons; therefore, it is oxidized.

Which of the following is true in redox reactions? Both oxidizing and reducing agents are oxidized. The oxidizing agent is the substance oxidized. The reducing agent is the substance oxidized. The reducing agent is the substance reduced.

The reducing agent is the substance oxidized.

In a correctly balanced redox equation, how does the number of electrons lost in an oxidation compare with the number gained in the simultaneous reduction? The number lost is always less than the number gained. The two numbers are always equal. No relationship exists between the two numbers. The number lost is always greater than the number gained.

The two numbers are always equal.

What is the gain of electrons called? electrochemistry reduction half-reaction oxidation

reduction

A species whose oxidation number decreases in a reaction is said to be which of the following? electrolyzed auto-oxidized reduced oxidized

reduced

Determine the oxidation number of N in NO3-. +4 +6 +3 +5

+5

Determine the oxidation number of P in P2O5. +3 +2 +5 -2

+5

In the dichromate ion, Cr2O72-, the chromium has an oxidation number of what? -2 +7 +6 +12

+6

Determine the oxidation number of Mn in KMnO4. +6 -2 +1 +7

+7

Determine the oxidation number of S in Al2S3. +6 -3 +3 -2

-2

All free elements have an oxidation number of what? 0 -2 +1 -1

0

What does the algebraic sum of the oxidation numbers of the atoms in a compound always equal? -1 any whole number 0 +1

0

What is the most common oxidation number of hydrogen when combined with elements other than itself? -1 0 -2 +1

+1

All monatomic ions have oxidation numbers equal to what? the difference of protons and neutrons the number of electrons the difference of protons and electrons the number of protons

the difference of protons and electrons

After balancing the redox equation BrO2- + OH- + N2O4 → BrO3-+H2O + NO2-, what are the coefficients, in order from left to right? 1, 2, 2, 1, 1, 2 2, 2, 1, 1, 2, 2 1, 2, 1, 1, 1, 1 1, 2, 1, 1, 1, 2

1, 2, 1, 1, 1, 2

When the following redox equation is correctly balanced in acid, what is the coefficient of the H+? Cr2O72- + H+ + I- → Cr3+ + I2 + H2O 14 3 7 6

14

How many electrons are being exchanged in the balanced redox equation Pb + 2Ag+→ Pb2+ + 2Ag? 4 3 1 2

2

When the following redox equation is balanced correctly in acid, what is the coefficient of the HNO3? HNO3 + H3PO3→ H3PO4 + NO 3 2 4 1

2

When an automobile battery is starting a car, which of the following occurs? Energy of motion is converted to energy as heat. Electrical energy is converted to chemical energy. Chemical energy is converted to electrical energy. Energy as heat is converted to energy of motion.

Chemical energy is converted to electrical energy.

In the following equation, which species is oxidized? TiCl4(l) + O2(g) → TiO2(s) + 2Cl2(g) Ti Cl O TiO2

Cl

What is the oxidizing agent in the following oxidation-reduction equation? H+ + I- + Cr2O72-→ Cr3+ + I2 + H2 O Cr3+ Cr2O7^2- H+ I-

Cr2O7^2-

In the following equation, which species is the oxidizing agent? SiO2(s) + 2C(s) → Si(s) + 2CO(g) C SiO2 Si O

FOR SOME REASON IT'S NOT THE FIRST ONE... I THINK THEIR ANSWER IS WRONG BECAUSE CARBON SEEMS LIKE IT'S THE CORRECT ANSWER

What are the oxidation numbers in the compound H2O2? H = +1, O = -1 H = +2, O = -2 H = +1, O = -2 H = -1, O = -2

H = +1, O = -1

What is the reducing agent in the following oxidation-reduction equation? MnO4- + H2SO3 + H+→ Mn2+ + HSO4- + H2 O H2SO3 H+ H2 O MnO4-

H2SO3

Which of the following statements correctly describes the redox equation 6H+ + MnO4- + 5CO → 5CO2 + Mn2+ + 3H2O? 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 correctly balanced. It is not balanced for the number of atoms or charge.

It is not balanced for the number of atoms or charge.

In the reaction represented by the equation: Fe → Fe3+ + 3e-, what happens to the species Fe? It is oxidized. It is neutralized. It is made disproportionate. It is reduced.

It is oxidized.

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 base? OH- H2 O H+ none of these

OH-

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? metal electrode cathode reducing electrode anode

anode

Which substances react in the standard automobile battery? copper(II) oxide, copper, and sulfuric acid iron(III) oxide, iron, and sulfuric acid zinc oxide, zinc, and sulfuric acid lead(IV) oxide, lead, and sulfuric acid

lead(IV) oxide, lead, and sulfuric acid