AP Chem redox reactions and oxidation states key terms

What is a redox reaction?

A redox reaction involves the transfer of electrons between two species, resulting in oxidation and reduction.

Define oxidation.

Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.

Define reduction.

Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

True or False: Oxidation and reduction occur independently.

False. They occur simultaneously; when one species is oxidized, another must be reduced.

What are oxidizing agents?

Substances that accept electrons and are reduced in a redox reaction. Examples: $\displaystyle O_2$, $\displaystyle Cl_2$.

What are reducing agents?

Substances that donate electrons and are oxidized in a redox reaction. Examples: $\displaystyle H_2$, $\displaystyle Na$.

Fill in the blank: In a redox reaction, the substance that is oxidized _____ electrons.

loses

Example of a redox reaction?

The reaction between zinc and copper sulfate: $\displaystyle Zn + CuSO_4 → ZnSO_4 + Cu$.

What is the role of electrons in redox?

Electrons are transferred from the reducing agent to the oxidizing agent, facilitating oxidation and reduction.

Compare oxidation state and electron transfer.

Oxidation state indicates the charge on an atom. Electron transfer involves the movement of electrons in a redox reaction.

What does a half-reaction show?

A half-reaction shows either the oxidation or reduction process separately, indicating electron transfer.

True or False: All redox reactions involve oxygen.

False. Not all redox reactions involve oxygen; they involve the transfer of electrons.

What is an example of oxidation in everyday life?

Rusting of iron, where iron loses electrons to oxygen and forms iron oxide.

Fill in the blank: The oxidation state of an element in its elemental form is _____ .

0

What is a balanced redox reaction?

A balanced redox reaction has equal numbers of electrons lost in oxidation and gained in reduction.

Identify the oxidizing agent: $\displaystyle 2H_2 + O_2 → 2H_2O$.

Oxygen ($\displaystyle O_2$) is the oxidizing agent as it is reduced.

What is the oxidation state of oxygen in most compounds?

- Usually -2 - Exceptions: peroxides (-1), superoxides (-1/2)

Determine the oxidation state of sulfur in H₂SO₄.

Sulfur (S) has an oxidation state of +6.

True or False: A free element has an oxidation state of zero.

True. All elements in their standard state have an oxidation state of 0.

What is the oxidation state of hydrogen in most compounds?

- Usually +1 - Exception: metal hydrides (-1)

Fill in the blank: The sum of oxidation states in a neutral compound is ___.

0.

Compare oxidation states in NaCl and MgO.

- Na: +1, Cl: -1 - Mg: +2, O: -2

Identify the oxidation state of nitrogen in NH₃.

Nitrogen (N) has an oxidation state of -3.

What is the general rule for oxidation states of alkali metals?

Alkali metals (Group 1) have an oxidation state of +1 in compounds.

Cause → Effect: What happens when an atom increases its oxidation state?

It loses electrons, becoming oxidized.

How to determine oxidation states in polyatomic ions?

- Assign oxidation states based on known rules - Ensure total equals the ion's charge

True or False: Transition metals have fixed oxidation states.

False. Transition metals can have multiple oxidation states.

Calculate the oxidation state of carbon in CO₂.

Carbon (C) has an oxidation state of +4.

What is the oxidation state of a halogen in a compound?

- Usually -1 - Exceptions: if bonded to a more electronegative element.

Identify oxidation states in H₂O.

Hydrogen (H) is +1, Oxygen (O) is -2.

Fill in the blank: The oxidation state of an ion is equal to its ___.

Charge.

How do you assign oxidation states in a compound with multiple elements?

Use hierarchy rules: electronegativity, known states, and total charge balance.