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Questions and Answers
What is the primary reaction when Ni2+ interacts with H2DMG?
What is the primary reaction when Ni2+ interacts with H2DMG?
- A nickel hydroxide precipitate is formed.
- Ni(HDMG)2 is formed with liberation of H+ ions. (correct)
- H2DMG is oxidized to a higher oxidation state.
- Ni2+ is completely converted into nickel metal.
What is the temperature range required for heating the solution during the titration process?
What is the temperature range required for heating the solution during the titration process?
- 90 - 100 °C
- 80 - 90 °C (correct)
- 60 - 70 °C
- 70 - 80 °C
What is the solubility characteristic of the precipitate formed by Ni(HDMG)2?
What is the solubility characteristic of the precipitate formed by Ni(HDMG)2?
- Soluble in all organic solvents.
- Insoluble in mineral acids.
- Insoluble in dilute ammonia solution. (correct)
- Soluble in distilled water.
What indicates the end point of the titration during the procedure?
What indicates the end point of the titration during the procedure?
Why must an excess of H2DMG be avoided during the precipitation process?
Why must an excess of H2DMG be avoided during the precipitation process?
What should be done if the temperature of the solution falls below 60 °C during the titration?
What should be done if the temperature of the solution falls below 60 °C during the titration?
What is the impact of temperature on the precipitate formed from nickel(II) solutions?
What is the impact of temperature on the precipitate formed from nickel(II) solutions?
Which volume of sulfuric acid is recommended to be added to the H2O2 solution during the determination of volume strength?
Which volume of sulfuric acid is recommended to be added to the H2O2 solution during the determination of volume strength?
What type of complexes are formed when using organic reagents like dimethylglyoxime?
What type of complexes are formed when using organic reagents like dimethylglyoxime?
What is the main indicator used in the Mohr Method of titration?
What is the main indicator used in the Mohr Method of titration?
In what type of medium should the Mohr Method be conducted?
In what type of medium should the Mohr Method be conducted?
How is the concentration of the H2O2 solution determined in the procedure?
How is the concentration of the H2O2 solution determined in the procedure?
What is the main reason for adding the dimethylglyoxime solution in ethanol?
What is the main reason for adding the dimethylglyoxime solution in ethanol?
Which precipitate is formed first in the Mohr Method during titration?
Which precipitate is formed first in the Mohr Method during titration?
Which of the following ions could partially precipitate along with nickel ion under specified conditions?
Which of the following ions could partially precipitate along with nickel ion under specified conditions?
What characteristic do organic precipitants typically possess in terms of molecular weight?
What characteristic do organic precipitants typically possess in terms of molecular weight?
What is the primary purpose of the Volhard Method in titration?
What is the primary purpose of the Volhard Method in titration?
What is formed when Fe3+ reacts with SCN- in the Volhard titration?
What is formed when Fe3+ reacts with SCN- in the Volhard titration?
Which reaction describes the end point of the Volhard titration?
Which reaction describes the end point of the Volhard titration?
What issue may arise due to the use of a dilute chromate solution in the Mohr Method?
What issue may arise due to the use of a dilute chromate solution in the Mohr Method?
What type of reaction is described in the Volhard Method?
What type of reaction is described in the Volhard Method?
What is the purpose of heating the sample at red heat for 5 minutes in the gravimetric analysis?
What is the purpose of heating the sample at red heat for 5 minutes in the gravimetric analysis?
Among the following, which steps should be performed after the initial heating of the sample?
Among the following, which steps should be performed after the initial heating of the sample?
What is the significance of the $2 ext{ mg}$ (or $0.002 ext{ g}$) mass difference in the weighing step?
What is the significance of the $2 ext{ mg}$ (or $0.002 ext{ g}$) mass difference in the weighing step?
What role does dimethylglyoxime serve in the gravimetric determination of nickel?
What role does dimethylglyoxime serve in the gravimetric determination of nickel?
What is the final compound obtained after the gravimetric determination of nickel?
What is the final compound obtained after the gravimetric determination of nickel?
Why is the precipitate washed with cold water in the nickel determination?
Why is the precipitate washed with cold water in the nickel determination?
What is the primary measurement recorded on the data sheet during sulfate analysis?
What is the primary measurement recorded on the data sheet during sulfate analysis?
What is the main characteristic of the nickel compounds formed in this experiment?
What is the main characteristic of the nickel compounds formed in this experiment?
What is the volume strength of a solution if 1 g of H2O2 generates 329.2 mL of O2?
What is the volume strength of a solution if 1 g of H2O2 generates 329.2 mL of O2?
Which solution is primarily used to determine the percent weight of iron (as Fe2+) in an unknown sample?
Which solution is primarily used to determine the percent weight of iron (as Fe2+) in an unknown sample?
In the context of redox titration, how does potassium permanganate (MnO4-) function?
In the context of redox titration, how does potassium permanganate (MnO4-) function?
What is the relationship between the weight of H2O2 and the volume of O2 produced?
What is the relationship between the weight of H2O2 and the volume of O2 produced?
Which of these oxidants can be used for the determination of reducing agents by titration?
Which of these oxidants can be used for the determination of reducing agents by titration?
What is the standardization of KMnO4 typically done with?
What is the standardization of KMnO4 typically done with?
During the determination of Iron (III), what form is iron (II) oxidized to?
During the determination of Iron (III), what form is iron (II) oxidized to?
Which of the following indicates a reduction during titration?
Which of the following indicates a reduction during titration?
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Study Notes
Gravimetric Analysis of Sulfate
- Continue heating at red heat for 5 minutes, cool for 3 minutes, then transfer to a desiccator.
- Record mass after cooling and reheat for 5 minutes, repeating the cooling and weighing process.
- Mass should be consistent within 2 mg (0.002 g).
- Calculate percentage of sulfate (BaSO4) in the original sample.
- Create a formal laboratory report with all observations and data.
Data Sheet for Sulfate Analysis
- Enter volume of unknown solution and weight of empty crucible.
- Document weight of crucible with precipitate (BaSO4) and weight of BaSO4 alone.
- Note weight of sulfate ion (SO42-) and calculate its concentration in mg per liter.
Gravimetric Determination of Nickel
- Nickel determination involves precipitation using organic reagents to form colored, sparingly soluble compounds.
- Dimethylglyoxime (C4H7O2N2) is used to precipitate nickel from a hot, slightly acidic solution, generating a bright red precipitate.
- The precipitation reaction: Ni2+ + 2H2DMG → Ni(HDMG)2 + 2H+.
- Organic reagents form chelate complexes, aiding in selective precipitation.
- Precipitate characteristics: crystalline, good filterability, and washability, with stability up to 170°C.
Precipitation and Solubility
- The dimethylglyoxime precipitate is insoluble in dilute ammonia and slightly soluble in mineral acids.
- A 1% ethanolic solution of dimethylglyoxime suffices for precipitation of 2.5 mg of nickel.
- Excess reagent should be avoided to prevent complications with solubility.
Silver Determination Methods
- Mohr Method: Uses chromate as an indicator to detect silver ion presence. Requires neutral pH to prevent unwanted reactions.
- Volhard Method: Involves titration with SCN- and uses Fe3+ as an indicator to detect excess silver ions through back-titration, forming a red complex.
Titration Process for Fe2+ Determination
- Use a standard solution of potassium dichromate (K2Cr2O7) for oxidizing Fe2+ to Fe3+ in the presence of harsh oxidants.
- Various compounds can be analyzed through this standard titration method.
Oxidation-Reduction Reactions (Redox Titration)
- Strong oxidants such as permanganate and dichromate are essential for determining reducing agents, particularly iron (II).
- The experiment aims to calculate the weight percent of Fe2+ in an unknown sample using potassium dichromate.
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