Chapter 13: Redox Reactions:

Question 1

What is the most common chemical change in both living and non-living systems?

Answer 1

Electrochemical (electron transfer) reactions are the most common chemical reactions among both living and non-living systems.

Question 2

What is metallurgy?

Answer 2

The science and technology of extracting metals from their naturally occurring compounds and adapting these metals for useful purposes.

Question 3

In what form do most metals exist before being extracted?

Answer 3

Most metals exist in a variety of compounds mixed with other substances called ores. Very few metals (such as gold/silver) exist naturally in pure element form.

Question 4

What is half-reaction?

Answer 4

A half-reaction represents what is happening to one reactant in an overall reaction. It is a balanced chemical equation that represents either a loss or gain of electrons by a substance.

Question 5

What is reduction?

Answer 5

The gain of electrons.

Question 6

What is oxidation?

Answer 6

The loss of electrons.

Question 7

What is a redox reaction?

Answer 7

A chemical reaction in which electrons are transferred between entities.

Question 8

What to remember about redox reactions?

Answer 8

The number of electrons gained in reduction must equal the number of electrons lost in oxidation.

Question 9

What to do after studying flashcards?

Answer 9

Read through notebook problems/improve your notes, and then look through textbook problems.

Question 10

What are the steps to writing half-reaction equations?

Answer 10

1. Write chemical formula of reactants and products. 2. Balance all atoms, other than O and H. 3. Balance O by adding H2O(l). 4. Balance H by adding H+(aq). 5. Balance the charge on each side by adding e- and cancel anything that is same on both sides.

Question 11

What are the additional steps for balancing basic solution half-reaction equations?

Answer 11

6. Add OH-(aq) to both sides to equal the number of H+(aq) present. 7. Combine H+(aq) and OH-(aq) on the same side to form H2O(l).

Question 12

What is a reducing agent?

Answer 12

A substances that causes reduction by donating electrons to another substance. Reducing agents are oxidized.

Question 13

What is an oxidizing agent?

Answer 13

A substance that causes oxidation by removing electrons from another substance. Oxidizing agents are reduced.

Question 14

What is the tendency of the most reactive metal ions?

Answer 14

The most reactive metal ions have the greatest tendency to gain electrons/be reduced ( and become metals).

Question 15

What is the tendency of the most reactive metals?

Answer 15

The most reactive metals have the greatest tendency to lose electrons/be oxidized (and become ions).

Question 16

What is the redox spontaneity rule?

Answer 16

The redox spontaneity rule states that a spontaneous redox reaction occurs only if the oxidizing agent (OA) is above the reducing agent (RA) on the ‘table of relative strengths of oxidizing and reducing agents’. If the RA is above the OA on the table, this results in a non-spontaneous reaction.

Question 17

What is disproportionation?

Answer 17

When a substance is both the SOA and SRA.

Question 18

Steps for predicting redox reactions?

Answer 18

1. List all entities present and label each as possible OAs/RAs or both (DO NOT label specator ions). 2. Choose SOA using given redox table, and write equation for it’s REDUCTION. 3. Choose SRA using given redox table, and write equation for it’s OXIDATION. 4. Balance number of electrons lost/gained in half-reaction equations by multiplying both equations. Then add 2 half-reactions to obtain net ionic equation. 5. Using spontaneity rule, predict whether the net ionic equation represents a spontaneous or non-spontaneous reaction.

Question 19

What is an oxidation number?

Answer 19

A positive or negative number corresponding to the oxidation state assigned to an atom. They are written with the positive/negative sign in front of the number.

Question 20

What is oxidation state?

Answer 20

The electric charge an atom would have if electron pairs belonged entirely to the more electronegative atom.

Question 21

What is the oxidation number of element atoms?

Answer 21

0. Ex- Na is 0, Cl in Cl2 is 0.

Question 22

What is the oxidation number of hydrogen in most compounds, except for hydrides?

Answer 22

H is usually +1. In hydrides (metalH), H is -1.

Question 23

What is the oxidation number of oxygen in most compounds, besides peroxides and fluorides?

Answer 23

Oxygen is -2 in most compounds. It is -1 in peroxides (ex- H2O2), and +1 or +2 in Fluorides (however needed to fill each octet of F).

Question 24

What is the oxidation number of monatomic ions?

Answer 24

The charge on the ion. Ex- Na+ is + 1 and S2- is -2.

Question 25

Steps in determining oxidation numbers?

Answer 25

1. Assign common oxidation numbers. 2. The sum of the total oxidation numbers of atoms in a molecule or ion MUST equal the value of the net electric charge of the molecule or ion (the sum of oxidation numbers of a compound is 0, while the sum of oxidation numbers for a polyatomic ion is the charge on ion). 3. Any unknown oxidation number is determined logically based on known oxidation numbers and net charges.

Question 26

From the perspective of oxidation numbers, what is oxidation?

Answer 26

Oxidation is an increase’ (less negative) in oxidation number.

Question 27

From the perspective of oxidation numbers, what is reduction?

Answer 27

Reduction is a ‘decrease’ (more negative) of oxidation number.

Question 28

From the perspective of oxidation numbers, what is a redox reaction?

Answer 28

A chemical reaction in which electrons are transferred and the oxidation numbers change (NO change in oxidation number= no redox reaction).

Question 29

What to remember when balancing redox reactions using oxidation numbers?

Answer 29

The total increase in oxidation number of an atom/ion must equal the total decrease in oxidation number decrease of another atom/ion.

Question 30

Steps to balancing Redox equations using oxidation numbers?

Answer 30

1. Assign oxidation numbers and identify atoms/ions whose oxidation numbers change. 2. Using the change in oxidation numbers, write the number of electrons transferred per atom. 3. Using the chemical formulas, determine the number of electrons transferred per reactant. 4. Calculate whole number coefficients that will balance total number of electrons transferred. Balance reactants/products. 5. Balance O atoms using H2O(l), and then balance the H atoms using H+(aq). Typical additional steps for basic solutions.

Question 31

What is the titrant in redox titrations?

Answer 31

The titrant (entity being added) is always a strong oxidizing or reducing agent.

Question 32

What is a primary standard?

Answer 32

A chemical that can be used directly to prepare a standard solution (a solution of accurately-known concentration).

Question 33

How do most metals exist in nature?

Answer 33

In their oxidized states, as metal oxides.

Question 34

What is the name of the rapid corrosion of a metal?

Answer 34

Combustion

Question 35

What to remember when finding SOA/SRA in questions?

Answer 35

Spectator ions DO NOT take part in the reaction, and are therefore ignored.

Question 36

What to do for titration questions?

Answer 36

List all entities present, find SOA/SRA then their reduction/oxidation reactions from table, separate and cancel out electrons, then do stoich from net equation.