We have provided 50 MCQs on Precipitation Titrations Unit-3, 1st semester, Pharmaceutical Analysis, B. Pharm.
We have covered following topics.
Precipitation titrations: Mohr’s method, Volhard’s, Modified Volhard’s, Fajans method, estimation of sodium Chloride.
Table of Contents
MCQ on Precipitation Titrations
- Which method of precipitation titration is commonly used for the estimation of chloride ions?
- A) Mohr’s method
- B) Volhard’s method
- C) Fajans method
- D) Modified Volhard’s method
Correct Answer: A) Mohr’s method
- In Mohr’s method, what is the titrant (precipitating agent) typically used to determine chloride ions?
- A) Silver nitrate (AgNO3)
- B) Sodium chloride (NaCl)
- C) Potassium dichromate (K2Cr2O7)
- D) Barium sulfate (BaSO4)
Correct Answer: A) Silver nitrate (AgNO3)
- Which indicator is commonly used in Mohr’s method to detect the endpoint of the titration between silver nitrate and chloride ions?
- A) Phenolphthalein
- B) Methyl orange
- C) Potassium dichromate
- D) Potassium chromate
Correct Answer: D) Potassium chromate
- Volhard’s method is primarily used for the titration of which type of ions in a solution?
- A) Chloride ions
- B) Sodium ions
- C) Iodide ions
- D) Sulfate ions
Correct Answer: C) Iodide ions
- What is the titrant (precipitating agent) used in Volhard’s method to determine iodide ions?
- A) Sodium chloride (NaCl)
- B) Silver nitrate (AgNO3)
- C) Potassium iodate (KIO3)
- D) Potassium dichromate (K2Cr2O7)
Correct Answer: B) Silver nitrate (AgNO3)
- In Volhard’s method, what is added as an indicator to detect the endpoint of the titration when all iodide ions have reacted with silver ions?
- A) Methyl orange
- B) Phenolphthalein
- C) Starch solution
- D) Potassium chromate
- Correct Answer: C) Starch solution
- The Modified Volhard’s method is an improvement of the original Volhard’s method and is used for the titration of which ions?
- A) Chloride ions
- B) Iodide ions
- C) Bromide ions
- D) Sulfate ions
Correct Answer: A) Chloride ions
- In Modified Volhard’s method, what is typically used as an indicator to detect the endpoint of the titration between silver nitrate and chloride ions?
- A) Potassium chromate
- B) Phenolphthalein
- C) Starch solution
- D) Methyl orange
Correct Answer: B) Phenolphthalein
- Fajans method is commonly employed for the estimation of which ion in a solution?
- A) Chloride ions
- B) Bromide ions
- C) Iodide ions
- D) Sulfate ions
Correct Answer: B) Bromide ions
- In Fajans method, which indicator is often used to detect the endpoint of the titration between silver ions and bromide ions?
- A) Starch solution
- B) Phenolphthalein
- C) Methyl orange
- D) Potassium chromate
Correct Answer: A) Starch solution
- How can sodium chloride (NaCl) be estimated quantitatively using precipitation titration methods?
- A) By titrating with silver nitrate (AgNO3) and using a chloride ion indicator
- B) By titrating with potassium iodate (KIO3) and using starch as an indicator
- C) By titrating with potassium dichromate (K2Cr2O7) and using phenolphthalein as an indicator
- D) By titrating with sodium hydroxide (NaOH) and using methyl orange as an indicator
Correct Answer: A) By titrating with silver nitrate (AgNO3) and using a chloride ion indicator
- Which of the following methods is commonly used for the titration of chloride ions in a solution but does not require the use of an indicator?
- A) Mohr’s method
- B) Volhard’s method
- C) Fajans method
- D) Modified Volhard’s method
Correct Answer: D) Modified Volhard’s method
- In the estimation of sodium chloride using a precipitation titration method, what is the reaction that occurs when silver nitrate is added to the solution containing chloride ions?
- A) Formation of a red precipitate
- B) Formation of a white precipitate
- C) Formation of a blue color
- D) Formation of a yellow color
Correct Answer: B) Formation of a white precipitate
- In Fajans method, what characteristic property of the silver chloride (AgCl) precipitate is utilized to detect the endpoint of the titration?
- A) Change in color from white to red
- B) Change in color from white to yellow
- C) Change in color from white to blue
- D) Change in color from white to brown
Correct Answer: B) Change in color from white to yellow
- In Volhard’s method, what is the reaction that takes place when all iodide ions have reacted with silver ions at the endpoint?
- A) Formation of a red precipitate
- B) Formation of a brown precipitate
- C) Formation of a blue color
- D) Formation of a violet color
Correct Answer: C) Formation of a blue color
- In Modified Volhard’s method, what is the role of phenolphthalein as an indicator?
- A) It changes color when all chloride ions have reacted.
- B) It forms a red precipitate with chloride ions.
- C) It changes color from blue to white.
- D) It changes color from yellow to red.
Correct Answer: A) It changes color when all chloride ions have reacted.
- Which of the following titration methods is NOT commonly used for the estimation of halide ions (chloride, bromide, or iodide)?
- A) Mohr’s method
- B) Volhard’s method
- C) Karl Fischer titration
- D) Fajans method
Correct Answer: C) Karl Fischer titration
- What does the term “back titration” refer to in the context of precipitation titrations?
- A) A titration performed in reverse order, starting with the analyte solution
- B) A titration that takes place at the back of the laboratory
- C) A titration used for the estimation of sodium chloride
- D) A titration using a burette with markings on the back
Correct Answer: A) A titration performed in reverse order, starting with the analyte solution
- In Mohr’s method for chloride estimation, what should be added to the titrated solution just before the endpoint to ensure accuracy?
- A) Potassium chromate
- B) Methyl orange
- C) Starch solution
- D) Ammonium chloride
Correct Answer: D) Ammonium chloride
- Which of the following is a common issue or challenge in precipitation titrations, especially in cases involving the estimation of chloride ions?
- A) The need for a strong reducing agent
- B) The potential for interference from other ions
- C) The lack of suitable indicators
- D) The requirement for a high pH solution
Correct Answer: B) The potential for interference from other ions
- In the estimation of chloride ions using Mohr’s method, what is the role of potassium chromate (K2CrO4)?
- A) It acts as a reducing agent.
- B) It forms a red precipitate with chloride ions.
- C) It serves as an indicator for the endpoint.
- D) It prevents the formation of silver chloride (AgCl).
Correct Answer: C) It serves as an indicator for the endpoint.
- Which of the following methods relies on the formation of a colored complex to indicate the endpoint of the titration?
- A) Mohr’s method
- B) Volhard’s method
- C) Fajans method
- D) Modified Volhard’s method
Correct Answer: C) Fajans method
- What is the key advantage of using Modified Volhard’s method over Mohr’s method for chloride estimation?
- A) It requires a smaller volume of silver nitrate.
- B) It provides a more precise endpoint.
- C) It doesn’t require the use of an indicator.
- D) It can estimate chloride in the presence of other ions.
Correct Answer: D) It can estimate chloride in the presence of other ions.
- In Volhard’s method, what is the purpose of adding excess silver nitrate (AgNO3) solution initially?
- A) To ensure complete reaction with iodide ions
- B) To precipitate all chloride ions as silver chloride (AgCl)
- C) To form a colored complex with iodide ions
- D) To create a redox reaction with iodide ions
Correct Answer: B) To precipitate all chloride ions as silver chloride (AgCl)
- Which of the following is true about Fajans method for halide estimation?
- A) It uses a colorless indicator.
- B) It relies on the formation of a colored complex.
- C) It is primarily used for chloride estimation.
- D) It does not involve the use of silver ions.
Correct Answer: B) It relies on the formation of a colored complex.
- What is the primary difference between Karl Fischer titration and precipitation titrations like Mohr’s and Volhard’s methods?
- A) Karl Fischer titration uses iodine as the titrant.
- B) Karl Fischer titration is a volumetric titration.
- C) Karl Fischer titration is used for estimating halides.
- D) Karl Fischer titration measures water content, not ions.
Correct Answer: D) Karl Fischer titration measures water content, not ions.
- In Modified Volhard’s method, why is phenolphthalein used as an indicator even though it changes color before the endpoint?
- A) To ensure the endpoint is easily visible.
- B) To neutralize any excess silver ions.
- C) To provide a sharp change in color near the endpoint.
- D) To prevent the formation of a red precipitate.
Correct Answer: C) To provide a sharp change in color near the endpoint.
- In the estimation of sodium chloride using a precipitation titration, what is the role of silver ions (Ag+)?
- A) They act as the analyte.
- B) They form a complex with chloride ions.
- C) They serve as a reducing agent.
- D) They are the titrant.
Correct Answer: D) They are the titrant.
- Which of the following statements is true about precipitation titrations?
- A) They are commonly used for estimating water content.
- B) They always involve the use of an indicator.
- C) They are not suitable for determining the presence of halide ions.
- D) They rely on the formation of a precipitate to indicate the endpoint.
Correct Answer: D) They rely on the formation of a precipitate to indicate the endpoint.
- What is the primary challenge when estimating chloride ions in the presence of other anions using Modified Volhard’s method?
- A) The method is not suitable for such mixtures.
- B) Interference from other anions can affect accuracy.
- C) Excess silver nitrate is needed to compensate.
- D) The endpoint cannot be visually detected.
Correct Answer: B) Interference from other anions can affect accuracy.
- In the estimation of chloride ions using Mohr’s method, why is it important to maintain a slightly acidic pH in the solution?
- A) To prevent the formation of silver chloride (AgCl)
- B) To ensure the formation of a red precipitate
- C) To enhance the solubility of silver chloride (AgCl)
- D) To reduce the concentration of chloride ions
Correct Answer: C) To enhance the solubility of silver chloride (AgCl)
- Which of the following indicators is often used in the Modified Volhard’s method for chloride estimation?
- A) Phenolphthalein
- B) Methyl orange
- C) Starch solution
- D) Potassium chromate
Correct Answer: A) Phenolphthalein
- In the Fajans method, what is the role of a precipitating agent like ammonium hydroxide (NH4OH)?
- A) To form a complex with halide ions
- B) To convert halide ions to iodine molecules
- C) To enhance the solubility of silver chloride (AgCl)
- D) To act as an indicator for the endpoint
Correct Answer: A) To form a complex with halide ions
- Which of the following statements is true regarding the endpoint detection in Volhard’s method?
- A) It is visually detected by the change in color of the solution.
- B) It is signaled by the formation of a brown precipitate.
- C) It is achieved when all silver ions react with iodide ions.
- D) It requires the addition of starch solution as an indicator.
Correct Answer: A) It is visually detected by the change in color of the solution.
- What is the chemical formula for the precipitate formed in Modified Volhard’s method when chloride ions react with silver ions?
- A) AgBr
- B) Ag2CrO4
- C) Ag2S
- D) AgCl
Correct Answer: D) AgCl
- In the estimation of bromide ions using Fajans method, what is the color change of the solution that indicates the endpoint?
- A) White to brown
- B) Yellow to orange
- C) Red to blue
- D) White to yellow
Correct Answer: D) White to yellow
- In Karl Fischer titration, what is the titrant used for the determination of water content?
- A) Silver nitrate (AgNO3)
- B) Sulfuric acid (H2SO4)
- C) Iodine (I2) in pyridine solution
- D) Sodium thiosulfate (Na2S2O3)
Correct Answer: C) Iodine (I2) in pyridine solution
- Why is starch solution added as an indicator in the Volhard’s method for the estimation of iodide ions?
- A) To enhance the solubility of silver iodide (AgI)
- B) To provide a red color change at the endpoint
- C) To improve the accuracy of the titration
- D) To prevent the formation of a brown precipitate
Correct Answer: A) To enhance the solubility of silver iodide (AgI)
- What is the primary role of a back titration in precipitation titrations?
- A) To use a different titrant in the reverse direction
- B) To confirm the endpoint of the initial titration
- C) To neutralize any excess titrant
- D) To eliminate the need for an indicator
Correct Answer: B) To confirm the endpoint of the initial titration
- Which of the following ions forms a white precipitate with silver ions (Ag+) in precipitation titrations?
- A) Chloride ions (Cl⁻)
- B) Iodide ions (I⁻)
- C) Sulfate ions (SO4²⁻)
- D) Nitrate ions (NO3⁻)
Correct Answer: B) Iodide ions (I⁻)
- In the Modified Volhard’s method for chloride estimation, why is it essential to add excess silver nitrate (AgNO3) solution initially before the titration?
- A) To ensure the formation of a red precipitate
- B) To increase the sensitivity of the indicator
- C) To precipitate all chloride ions as silver chloride (AgCl)
- D) To enhance the accuracy of the endpoint detection
Correct Answer: C) To precipitate all chloride ions as silver chloride (AgCl)
- What is the main difference between the endpoint detection in Mohr’s method and Volhard’s method?
- A) Mohr’s method uses potassium chromate as an indicator, while Volhard’s method uses phenolphthalein.
- B) Mohr’s method involves a color change at the endpoint, while Volhard’s method uses starch to detect the endpoint.
- C) Mohr’s method relies on the formation of a red precipitate, while Volhard’s method has a colorless endpoint.
- D) Mohr’s method requires a back titration, while Volhard’s method does not.
Correct Answer: B) Mohr’s method involves a color change at the endpoint, while Volhard’s method uses starch to detect the endpoint.
- In the estimation of bromide ions using Fajans method, what type of complex forms when silver ions (Ag+) react with bromide ions (Br⁻)?
- A) Red complex
- B) Brown complex
- C) White complex
- D) Yellow complex
Correct Answer: D) Yellow complex
- Why is the use of a back titration particularly advantageous in Modified Volhard’s method?
- A) It allows for the estimation of chloride ions in the presence of other halides.
- B) It reduces the volume of silver nitrate needed.
- C) It eliminates the need for an indicator.
- D) It speeds up the titration process.
Correct Answer: A) It allows for the estimation of chloride ions in the presence of other halides.
- Which of the following statements is accurate regarding precipitation titrations?
- A) They always require the use of a colorless indicator.
- B) They involve the conversion of ions to a gas phase.
- C) They rely on the formation of a solid precipitate for endpoint detection.
- D) They are limited to the estimation of metal ions only.
Correct Answer: C) They rely on the formation of a solid precipitate for endpoint detection.
- In Volhard’s method, what role does iodide ions (I⁻) play in the titration process?
- A) They form a colored complex with silver ions.
- B) They reduce silver ions to metallic silver.
- C) They serve as a reducing agent for other ions.
- D) They precipitate as silver iodide (AgI) at the endpoint.
Correct Answer: B) They reduce silver ions to metallic silver.
- What is the primary reason for the use of excess silver nitrate (AgNO3) in Mohr’s method?
- A) To enhance the sensitivity of the indicator.
- B) To ensure that all chloride ions react and form silver chloride (AgCl).
- C) To reduce the solubility of silver chloride (AgCl).
- D) To create a colored complex with chloride ions.
Correct Answer: B) To ensure that all chloride ions react and form silver chloride (AgCl).
- In Fajans method, which substance forms a stable complex with halide ions (Cl⁻, Br⁻, I⁻)?
- A) Starch
- B) Ammonium hydroxide (NH4OH)
- C) Silver nitrate (AgNO3)
- D) Potassium chromate (K2CrO4)
Correct Answer: B) Ammonium hydroxide (NH4OH)
- What is the primary purpose of a blank titration in the context of precipitation titrations?
- A) To determine the solubility of the precipitate.
- B) To assess the potential interference from the titrant.
- C) To confirm the accuracy of the indicator.
- D) To adjust the pH of the solution.
Correct Answer: B) To assess the potential interference from the titrant.
- Which of the following substances does NOT typically form a precipitate in precipitation titrations?
- A) Silver chloride (AgCl)
- B) Silver bromide (AgBr)
- C) Silver iodide (AgI)
- D) Silver sulfate (Ag2SO4)
Correct Answer: D) Silver sulfate (Ag2SO4)
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