Module 3: Electrochemical Reactions Flashcards
Explain the difference between a reducing agent and an oxidizing agent using an example.
Reducing agent: substance that donates electrons and gets oxidized.
Oxidizing agent :substance that gains elections and gets reduced
Ex: When forming water hydrogen is the reducing agent, donating elections to oxygen which is the oxidizing agent
What is the redox spontaneity rule?
It states that a spontaneous redox reaction only occurs if the oxidizing agent is listed above the reducing agent in a redox table
Oxidation and reduction are processes, and oxidizing agents and reducing agents are substances. Explain this statement.
Oxidation and reduction refer to the process of electron transfer; oxidizing and reducing agents refer to species that gain or lose electrons in an electrochemical process.
If a substance is a very strong oxidizing agent, what does this mean in terms of electrons?
Strong oxidizing agents have a strong affinity for electrons and promote the loss of electrons by other substances during a reaction.
If a substance is a very strong reducing agent, what does this mean in terms of electrons?
Strong reducing agents have a weak affinity for electrons and tend to lose electrons to other substances during a reaction.
Use the redox spontaneity rule to predict whether the following mixtures will show evidence of a reaction; that is, predict whether the reactions are spontaneous. (Do not write the equations for the reaction.)
a) nickel metal in a solution of silver ions
b) zinc metal in a solution of aluminum ions
c) an aqueous mixture of copper(II) ions and iodide ions
d) chlorine gas bubbled into a bromide ion solution
e) an aqueous mixture of copper(II) ions and tin(II) ions
f) copper metal in nitric acid
Use the redox spontaneity rule to predict whether the following mixtures will show evidence of a reaction; that is, predict whether the reactions are spontaneous. (Do not write the equations for the reaction.)
a) nickel metal in a solution of silver ions S
b) zinc metal in a solution of aluminum ions NS
c) an aqueous mixture of copper(II) ions and iodide ions. NS
d) chlorine gas bubbled into a bromide ion solution. S
e) an aqueous mixture of copper(II) ions and tin(II) ions S
f) copper metal in nitric acid S
Five-Step Method for Predicting Redox Reactions
Step 1: List all entities present and classify each as a possible oxidizing agent, reducing agent, or both. Do not label spectator ions.
Step 2: Choose the strongest oxidizing agent as indicated in a redox table, and write the equation for its reduction.
Step 3: Choose the strongest reducing agent as indicated in the table, and write the equation for its oxidation.
Step 4: Balance the number of electrons lost and gained in the half-reaction equations by multiplying one or both equations by a number. Then add the two balanced half-reaction equations to obtain a net ionic equation.
Step 5: Using the spontaneity rule, predict whether the net ionic equation represents a spontaneous or non-spontaneous redox reaction.
Complete the half-reaction equation and classify it as an
oxidation or a reduction.
dinitrogen oxide to nitrogen gas in an acidic solution
complete the half-reaction equation and classify it as an
oxidation or a reduction.
nitrite ions to nitrate ions in a basic solution
complete the half-reaction equation and classify it as an
oxidation or a reduction.
silver(I) oxide to silver metal in a basic solution
complete the half-reaction equation and classify it as an
oxidation or a reduction.
nitrate ions to nitrous acid in an acidic solution
complete the half-reaction equation and classify it as an
oxidation or a reduction.
hydrogen gas to water in a basic solution
Use the five-step method to predict the most likely redox reaction in each of the following situations. For any spontaneous reaction, describe one diagnostic test to identify a primary product.
During a demonstration, zinc metal is placed in a hydrochloric acid solution.
Use the five-step method to predict the most likely redox reaction in each of the following situations. For any spontaneous reaction, describe one diagnostic test to identify a primary product.
A gold ring accidentally falls into a hydrochloric acid solution.
Use the five-step method to predict the most likely redox reaction in each of the following situations. For any spontaneous reaction, describe one diagnostic test to identify a primary product.
Nitric acid is painted onto a copper sheet to etch a design.
How do you balance a redox reaction in an acidic solution?
- Assign oxidation numbers and identify atoms/ions with changes.
- Calculate electrons transferred per atom.
- Calculate total electrons transferred per reactant (use subscripts).
- Balance electrons using whole number coefficients.
- Balance oxygen using H₂O and hydrogen using H⁺
How do you balance a redox reaction in a basic solution?
- Assign oxidation numbers and identify atoms/ions with changes.
- Calculate electrons transferred per atom.
- Calculate total electrons transferred per reactant (use subscripts).
- Balance electrons using whole number coefficients.
- Balance oxygen using H₂O and hydrogen using H⁺
- Add OH⁻ equal to H⁺ on both sides.
- Combine H⁺ and OH⁻ to form H₂O then cancel excess water.
Determine the oxidation number
Carbon can be progressively oxidized in a series of organic reactions. Determine the oxidation number of carbon in each of the compounds in the following series of oxidations:
Assign oxidation numbers to the atoms/ions in each of the following by completing the table.
Draw a titration setup, labelling the following parts:
burette, Erlenmeyer flask, sample, titrant
What four assumptions must we make when performing a redox titration?
- spontaneous
- fast
- stoichiometric
- quantitative
Explain what a standard solution is and why some substances have to be re-standardized as time progresses.
A standard solution is a solution where the
concentration is accurately known. Some substances
may continue to react as time progresses due to
evaporation or temperature changes.
B
B
1003
B
D
A
D
B
1984
12.8
- A
- D
- B
5876
