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Role of NH4Cl in qualitative analysis of third group cations
- a)to provide basic medium
- b)to provide acidic medium
- c)to increase the degree of dissociation of NH4OH
- d)to suppress the degree of dissociation of NH4OH
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
Role of NH4Cl in qualitative analysis of third group cationsa)to provi...
The correct answer is option D
Common ion effect is observed when a solution of weak electrolyte is mixed with a solution of strong electrolyte, which provides an ion common to that provided by weak electrolyte.
The NH4OH is a weak base and it does not ionise completely. Thus, due to presence of common ion NH4+ in NH4Cl, it suppresses the ionisation of weak base NH4OH in order to decrease the OH- concentration so that higher group cations will not get precipitated.
Thus the pair NH4OH+NH4Cl shows a common ion effect.
Ammonium chloride suppresses the ionization of ammonium hydroxide
.
Common ion effect is observed when a solution of weak electrolyte is mixed with a solution of strong electrolyte, which provides an ion common to that provided by weak electrolyte.
The NH4OH is a weak base and it does not ionise completely. Thus, due to presence of common ion NH4+ in NH4Cl, it suppresses the ionisation of weak base NH4OH in order to decrease the OH- concentration so that higher group cations will not get precipitated.
Thus the pair NH4OH+NH4Cl shows a common ion effect.
Ammonium chloride suppresses the ionization of ammonium hydroxide
.
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Role of NH4Cl in qualitative analysis of third group cationsa)to provi...
Role of NH4Cl in qualitative analysis of third group cations:
The qualitative analysis of cations involves the identification and separation of different cations present in a given sample. The third group cations, which include Fe3+, Al3+, and Cr3+, are usually precipitated as hydroxides by adding ammonium hydroxide (NH4OH) in the presence of NH4Cl. NH4Cl plays a crucial role in this process. The correct answer is option 'D', which states that NH4Cl suppresses the degree of dissociation of NH4OH. Let's understand why this is the case.
1. Formation of hydroxide precipitates:
When NH4OH is added to the solution containing the third group cations, hydroxide precipitates are formed. The hydroxides of Fe3+, Al3+, and Cr3+ are Fe(OH)3, Al(OH)3, and Cr(OH)3 respectively. These precipitates are insoluble in water and appear as a solid precipitate.
2. Role of NH4Cl:
NH4Cl is added to the solution along with NH4OH to maintain a specific pH and prevent the precipitation of other cations. It serves the following purposes:
- Suppressing the degree of dissociation of NH4OH: The addition of NH4Cl suppresses the dissociation of NH4OH into NH4+ and OH- ions. This is because NH4Cl is a strong electrolyte and undergoes complete dissociation into NH4+ and Cl- ions. The presence of a large concentration of NH4+ ions shifts the equilibrium of NH4OH dissociation to the left, reducing the concentration of OH- ions. As a result, the formation of hydroxide precipitates is favored.
- Preventing the precipitation of other cations: NH4Cl also prevents the precipitation of other cations, such as Group 1 cations (Li+, Na+, K+, etc.), Group 2 cations (Mg2+, Ca2+, etc.), and Group 4 cations (Mn2+, Zn2+, etc.). This is because NH4Cl forms soluble complexes with these cations, keeping them in solution instead of forming insoluble hydroxides.
Conclusion:
In the qualitative analysis of third group cations, NH4Cl is added to suppress the degree of dissociation of NH4OH. This leads to the formation of hydroxide precipitates of Fe3+, Al3+, and Cr3+. NH4Cl also prevents the precipitation of other cations by forming soluble complexes.
The qualitative analysis of cations involves the identification and separation of different cations present in a given sample. The third group cations, which include Fe3+, Al3+, and Cr3+, are usually precipitated as hydroxides by adding ammonium hydroxide (NH4OH) in the presence of NH4Cl. NH4Cl plays a crucial role in this process. The correct answer is option 'D', which states that NH4Cl suppresses the degree of dissociation of NH4OH. Let's understand why this is the case.
1. Formation of hydroxide precipitates:
When NH4OH is added to the solution containing the third group cations, hydroxide precipitates are formed. The hydroxides of Fe3+, Al3+, and Cr3+ are Fe(OH)3, Al(OH)3, and Cr(OH)3 respectively. These precipitates are insoluble in water and appear as a solid precipitate.
2. Role of NH4Cl:
NH4Cl is added to the solution along with NH4OH to maintain a specific pH and prevent the precipitation of other cations. It serves the following purposes:
- Suppressing the degree of dissociation of NH4OH: The addition of NH4Cl suppresses the dissociation of NH4OH into NH4+ and OH- ions. This is because NH4Cl is a strong electrolyte and undergoes complete dissociation into NH4+ and Cl- ions. The presence of a large concentration of NH4+ ions shifts the equilibrium of NH4OH dissociation to the left, reducing the concentration of OH- ions. As a result, the formation of hydroxide precipitates is favored.
- Preventing the precipitation of other cations: NH4Cl also prevents the precipitation of other cations, such as Group 1 cations (Li+, Na+, K+, etc.), Group 2 cations (Mg2+, Ca2+, etc.), and Group 4 cations (Mn2+, Zn2+, etc.). This is because NH4Cl forms soluble complexes with these cations, keeping them in solution instead of forming insoluble hydroxides.
Conclusion:
In the qualitative analysis of third group cations, NH4Cl is added to suppress the degree of dissociation of NH4OH. This leads to the formation of hydroxide precipitates of Fe3+, Al3+, and Cr3+. NH4Cl also prevents the precipitation of other cations by forming soluble complexes.
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Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer? for Class 11 2025 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 11 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer?.
Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer? for Class 11 2025 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 11 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer?.
Solutions for Role of NH4Cl in qualitative analysis of third group cationsa)to provide basic mediumb)to provide acidic mediumc)to increase the degree of dissociation of NH4OHd)to suppress the degree of dissociation of NH4OHCorrect answer is option 'D'. Can you explain this answer? in English & in Hindi are available as part of our courses for Class 11.
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