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Questions and Answers
What color change indicates the endpoint in a titration involving KMnO₄?
What color change indicates the endpoint in a titration involving KMnO₄?
- Colorless to yellow
- Purple to colorless (correct)
- Green to blue
- Colorless to purple
Which statement is true regarding potassium dichromate (K₂Cr₂O₇)?
Which statement is true regarding potassium dichromate (K₂Cr₂O₇)?
- It requires external indicators for titration. (correct)
- It is a stronger oxidizing agent than KMnO₄.
- It can oxidize I⁻ to I₂ without additional agents.
- It serves as a self-indicator.
What reaction occurs during iodimetric titrations involving Cu²⁺ ions?
What reaction occurs during iodimetric titrations involving Cu²⁺ ions?
- 2Cu²⁺(aq) + 4I⁻(aq) → Cu₂I₂(s) + I₂(aq) (correct)
- I₂(aq) + 4H⁺(aq) + 2e⁻ → 2I⁻(aq) + 2H₂O(l)
- Cu²⁺(aq) + I₂(aq) → CuI₂(s)
- I₂(aq) + S₂O₃²⁻(aq) → Na₂S₄O₆(aq) + 2I⁻(aq)
What is the equivalent weight of KMnO₄ when used in acidic medium?
What is the equivalent weight of KMnO₄ when used in acidic medium?
Which oxidizing agent is used specifically for titrating strong reducing agents like sodium thiosulphate?
Which oxidizing agent is used specifically for titrating strong reducing agents like sodium thiosulphate?
What role does freshly prepared starch solution play in iodimetric titrations?
What role does freshly prepared starch solution play in iodimetric titrations?
Which oxidizing agent is characterized as a self-indicator?
Which oxidizing agent is characterized as a self-indicator?
In iodimetric titrations, released iodine (I₂) is titrated against which solution?
In iodimetric titrations, released iodine (I₂) is titrated against which solution?
Flashcards
KMnO₄ in titration
KMnO₄ in titration
Potassium permanganate (KMnO₄) is a strong oxidizing agent used in titrations. It acts as a self-indicator, changing color from purple to colorless during the reaction.
Acidified K₂Cr₂O₇
Acidified K₂Cr₂O₇
Acidified potassium dichromate (K₂Cr₂O₇) is a weaker oxidizing agent used in redox titrations but needs external indicators.
Iodine (I₂) titration
Iodine (I₂) titration
Iodine (I₂) is a mild oxidizing agent used in titrations, especially with strong reducing agents like sodium thiosulfate.
Iodimetric titration
Iodimetric titration
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Iodometric titration
Iodometric titration
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Equivalent weight (Eq. wt.)
Equivalent weight (Eq. wt.)
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Endpoint detection (I₂)
Endpoint detection (I₂)
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Redox titration
Redox titration
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Study Notes
Oxidation Reactions as the Basis of Titrations
- Potassium permanganate (KMnO4) is a strong oxidizing agent
- In titrations, KMnO4 acts as a self-indicator; its color disappears when it reacts with a reducing agent.
- The reaction for the titration of MnO4- against Fe2+ ions is: MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
- Acidified potassium dichromate (K2Cr2O7) is a weaker oxidizing agent than KMnO4
- It does not act as a self-indicator; indicators like diphenylamine or potassium ferricyanide (K3[Fe(CN)6]) are used
- The chemical equation for K2Cr2O7 as an oxidizing agent is: Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O
Iodine (I2)
- Iodine is a mild oxidizing agent
- The reaction is: I2 + 2e- → 2I-
- Iodine is used in titrations with strong reducing agents like sodium thiosulfate (Na2S2O3)
- The reaction is: I2(aq) + 2S2O32-(aq) → 2I-(aq) + S4O62-(aq)
Iodimetric and Iodometric Titrations
- Iodimetric titrations: Iodine (I2) is directly titrated against a reducing agent
- Iodometric titrations: Iodine is liberated from KI by an oxidizing agent, and the liberated iodine is then titrated against a standard solution of sodium thiosulfate (Na2S2O3)
- The end point of iodimetric titrations is detected using a starch solution, which reacts with iodine to form an intensely blue-colored complex
Note
- Equivalent weight (Eq. wt.) of an oxidizing or reducing agent = Mol. wt / Change in oxidation state or number of electrons gained or lost
- Example: Eq. wt. of KMnO4 in an acidic medium = 158/5 = 31.6
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Description
Explore the fundamentals of oxidation reactions as they apply to titrations, highlighting the role of strong oxidizing agents such as potassium permanganate and potassium dichromate. Understand the self-indicating properties of KMnO4 and the use of indicators with K2Cr2O7. This quiz will test your knowledge of these important chemical processes.
