Redox Reactions: Energy-Producing Reactions at the Molecular Level of Life

Flashcards covering key definitions, rules for oxidation numbers, and general principles of balancing redox reactions from the lecture notes on Medicinal and Pharmaceutical Chemistry.

What is an energy-producing reaction at the molecular level of life?

A redox reaction.

What are the three major purposes for which energy is required in the human body?

Muscle contraction and other cellular movements; Active transport of molecules and ions; Synthesis of macromolecules and other biomolecules from simple precursors.

What is the fundamental way of energy exchange in biological systems?

The ATP-ADP cycle.

When does oxidation occur in a molecule?

When a molecule loses electrons, loses hydrogen, or gains oxygen.

If a molecule undergoes oxidation, what is it said to be?

The reducing agent.

When does reduction occur in a molecule?

When a molecule gains electrons, gains hydrogen, or loses oxygen.

If a molecule undergoes reduction, what is it said to be?

The oxidizing agent.

In the reaction Zn(s) + CuSO4(aq) at ZnSO4(aq) + Cu(s), which species is oxidized?

Zn (Zinc).

In the reaction Zn(s) + CuSO4(aq) at ZnSO4(aq) + Cu(s), which species is reduced?

Cu2+ (Copper ion).

In the reaction Zn(s) + CuSO4(aq) at ZnSO4(aq) + Cu(s), which species is the reducing agent?

Zn (Zinc).

In the reaction Zn(s) + CuSO4(aq) at ZnSO4(aq) + Cu(s), which species is the oxidizing agent?

Cu2+ (Copper ion).

What is an oxidation number (or oxidation state)?

The charge an atom would have in a molecule or ionic compound if electrons were transferred completely.

According to the rules for assigning oxidation numbers, what is the oxidation number of free elements?

Zero.

According to the rules for assigning oxidation numbers, what is the oxidation number of a monatomic ion?

It is equal to the charge on the ion.

What is the usual oxidation number of oxygen, and what are its exceptions?

Usually at -2; In H2O2 and O22- it is -1, and in superoxide ion (O2-) it is -½.

What is the usual oxidation number of hydrogen, and what is its exception?

Usually at +1; except when it is bonded to metals in binary compounds, where it is -1.

What are the oxidation numbers for Group IA metals, Group IIA metals, and fluorine?

Group IA metals are +1, Group IIA metals are +2, and fluorine is always -1.

What is the rule for the sum of the oxidation numbers of all atoms in a molecule or ion?

The sum is equal to the charge on the molecule or ion.

What is the overall balanced equation for the breakdown of glucose in the body to produce energy (cellular respiration)?

C6H12O6 + 6O2 at 6CO2 + 6H2O + Energy.

What is the first step when balancing redox reactions?

Determine what is being oxidised and what is being reduced.

How are oxygen and hydrogen atoms balanced in redox reactions in an acidic medium?

Add H2O to balance O atoms and H+ to balance H atoms.

What additional step is required to balance redox reactions in a basic medium, after balancing O and H with H2O and H+?

For every H+ ion, add an equal number of OH- ions to both sides of the equation.