27 Questions
Which statement best describes the relationship between solubility product constant (Ksp) and solubility?
A higher Ksp indicates a more soluble compound.
Based on the text, which of the following cations has the highest solubility in water?
Ag+
Why is the color examination of the unknown solution limited?
Concentration affects color perception.
Which of the following statements about lead chloride is accurate based on the text?
Lead chloride may not be precipitated at all in low concentrations.
What role do good organizational skills and techniques play in achieving correct results in this lab?
They are essential for accurate outcomes.
In terms of solubility, which compound would most likely exhibit the highest degree of dissociation in water?
Silver chloride
What is the purpose of precipitating the group with dilute HCl?
To separate the cations when they become chlorides
Why is hot water used in the leaching step to remove Lead chloride?
To increase the solubility of Lead chloride
What is the risk associated with not properly separating Lead chloride in Procedure 2?
Confusion in making identification tests for silver and mercurous ions
What is the purpose of Procedure 2A: Separation and Identification of Lead Ion?
To separate and identify Lead ions from other cations
What serves as a medium for the auto-redox action of Hg2Cl2 in the presence of ammonia water?
HgNH2Cl
What type of precipitate indicates the presence of mercurous ions?
Gray
What color is metallic mercury in a finely divided state?
Black
What chemical reagent is used as a precipitating agent for the separation and identification of mercurous ions?
Stannous chloride
Which experimental result indicates the presence of silver ions in unknown samples 1 and 3?
White precipitate
What is the purpose of having a 'waste' beaker near the work area?
To discard waste solutions locally
How can students test the pH of a solution using litmus paper?
By dipping a stirring rod into the solution and then touching it to the litmus paper
What is indicated by the appearance or disappearance of a color in a solution or in a flame?
A positive test
Why is cross-contamination considered a common cause for false observations?
It leads to incorrect conclusions
What should students do before reusing glassware according to the text?
Clean out and rinse all glassware with deionized water
How can students know if a solution is acidic using litmus paper?
It will turn blue litmus paper red
What is the chemical formula of the yellow precipitate formed when lead (II) ions react with potassium chromate?
PbCrO4
Which unknown sample did not show any precipitation form during the experimental results?
Unknown sample 1
In the procedure for the separation and identification of silver ions, what color does the precipitate turn into after the addition of nitric acid?
White
What is the role of dilute ammonia in the separation of silver and mercurous ions?
It dissolves silver and forms a soluble complex with mercury
What determines the efficiency of separating silver chloride from mercurous chloride using ammonia?
The concentration of ammonia and the amount of AgCl
What happens when AgCl reacts with 2NH3 in the presence of H3O+?
Formation of white precipitate (AgCl)
Study Notes
Solubility and Solubility Product Constant (Ksp)
- A higher solubility product constant (Ksp) indicates a higher solubility in water.
- The cation with the highest solubility in water is silver (Ag+).
Color Examination Limitations
- The color examination of the unknown solution is limited because some ions may not exhibit distinct colors.
Lead Chloride
- Lead chloride (PbCl2) is highly soluble in hot water.
Importance of Organizational Skills
- Good organizational skills and techniques are crucial for achieving correct results in the lab to avoid contamination and mix-ups.
Solubility and Dissociation
- The compound that would most likely exhibit the highest degree of dissociation in water is silver chloride (AgCl).
Precipitation and Separation
- The purpose of precipitating the group with dilute HCl is to separate and identify the ions.
- Hot water is used in the leaching step to remove Lead chloride (PbCl2) because it is highly soluble in hot water.
Risks and Consequences
- The risk associated with not properly separating Lead chloride in Procedure 2 is contamination and incorrect results.
Procedure 2A: Separation and Identification of Lead Ion
- The purpose of Procedure 2A is to separate and identify the Lead ion (Pb2+).
Auto-Redox Action of Hg2Cl2
- Ammonia water serves as a medium for the auto-redox action of Hg2Cl2.
Mercurous Ions
- A white precipitate indicates the presence of mercurous ions (Hg2+).
- Metallic mercury is white in a finely divided state.
Precipitating Agent
- The chemical reagent used as a precipitating agent for the separation and identification of mercurous ions is ammonia water.
Experimental Results
- A cream-colored precipitate indicates the presence of silver ions in unknown samples 1 and 3.
Laboratory Safety
- The purpose of having a 'waste' beaker near the work area is to minimize the risk of contamination.
pH Testing
- To test the pH of a solution using litmus paper, students can observe the color change of the paper.
Color Indicators
- The appearance or disappearance of a color in a solution or in a flame indicates the presence or absence of specific ions.
Cross-Contamination
- Cross-contamination is a common cause for false observations because it can lead to the mixing of ions or substances.
Laboratory Procedures
- Students should wash their glassware thoroughly before reusing it to avoid contamination.
Acidic Solutions
- A red color on litmus paper indicates that a solution is acidic.
Chemical Reactions
- The yellow precipitate formed when lead (II) ions react with potassium chromate has the chemical formula PbCrO4.
Experimental Results
- Unknown sample 2 did not show any precipitation during the experimental results.
Separation of Silver Ions
- The precipitate turns into a white color after the addition of nitric acid in the procedure for the separation and identification of silver ions.
Separation of Silver and Mercurous Ions
- Dilute ammonia is used to separate silver and mercurous ions because it reacts differently with each ion.
Efficiency of Separation
- The efficiency of separating silver chloride from mercurous chloride using ammonia depends on the concentration of ammonia and the reaction conditions.
Chemical Reaction
- When AgCl reacts with 2NH3 in the presence of H3O+, it forms a complex ion.
Test your knowledge on the procedures and principles of qualitative inorganic analysis. Learn about the steps involved in group precipitation and separation of different cations using specific reagents.
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