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Questions and Answers
What color precipitate indicates the presence of Mn2+ during the confirmation test?
What color precipitate indicates the presence of Mn2+ during the confirmation test?
To confirm the presence of Co2+, the solution should turn blue when treated with NH4SCN.
To confirm the presence of Co2+, the solution should turn blue when treated with NH4SCN.
True
What is the result if the precipitate formed is white during the confirmation test of Group V?
What is the result if the precipitate formed is white during the confirmation test of Group V?
The unknown may belong to Group V.
The precipitate formed when testing for Sr2+ is a _____ precipitate.
The precipitate formed when testing for Sr2+ is a _____ precipitate.
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Match the ions with their corresponding test results:
Match the ions with their corresponding test results:
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What is indicated by a bright yellow precipitate when KI is added to the new solution?
What is indicated by a bright yellow precipitate when KI is added to the new solution?
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A dirty green precipitate indicates the presence of Al3+.
A dirty green precipitate indicates the presence of Al3+.
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What is the color of the precipitate that confirms the presence of Ag2CrO4?
What is the color of the precipitate that confirms the presence of Ag2CrO4?
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The addition of dil. H2SO4 to new solution will form a white ppt of __________.
The addition of dil. H2SO4 to new solution will form a white ppt of __________.
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Which of the following steps involves the addition of K2CrO4?
Which of the following steps involves the addition of K2CrO4?
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Match the cation with its corresponding group:
Match the cation with its corresponding group:
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What ion is confirmed by a blood red complex with ammonium thiocyanate?
What ion is confirmed by a blood red complex with ammonium thiocyanate?
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The presence of a yellow solution after boiling indicates Cr3+.
The presence of a yellow solution after boiling indicates Cr3+.
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Study Notes
Cations Scheme Lab 8
- This lab outlines a scheme for identifying cations in a solution.
- The scheme involves multiple steps using various reagents to distinguish different cations.
- The scheme identifies cations in five groups (group I-V).
- Cations such as Ag+, Pb2+, Cd2+, Cu2+, Bi3+, Fe3+, Cr3+, Al3+, Zn2+, Mn2+, Co2+, Ni2+, Ba2+, Sr2+, and Ca2+ are examined.
Step I
- Adding hydrochloric acid (HCl) to an unknown solution can precipitate some cations (group I).
- Silver (Ag+) creates a pale yellow precipitate.
- Lead (Pb2+) produces a bright yellow precipitate.
- Further tests confirm these cations with reagents like potassium iodide (KI) and potassium chromate (K₂CrO₄).
Step II
- The solution remaining after Step I is tested for other cations (group II).
- Adding hydrogen sulfide (H₂S) to the solution will precipitate some cations.
- Cadmium (Cd²⁺), copper (Cu²⁺), and bismuth (Bi³⁺) are common examples
- Further tests distinguish between these cations (using ammonia and other reagents).
Step III
- The solution remaining after Step II is tested for further cations (group III).
- Ammonium chloride (NH₄Cl) and concentrated ammonia (NH₄OH) are typically used
- Iron (Fe³⁺), chromium (Cr³⁺), and aluminum(Al³⁺) are common cations.
- Different precipitates are observed when reagents are used.
Step IV
- The solution remaining after Step III is tested for further cations (group IV).
- Adding concentrated ammonia (NH₄OH), ammonium chloride (NH₄Cl) and hydrogen sulfide (H₂S) is typical here.
- The cations being sought include zinc (Zn²⁺), manganese (Mn²⁺), cobalt (Co²⁺), and nickel (Ni²⁺).
- Different colors and precipitates are observed.
Step V
- The solution remaining is tested for cations in the final group (group V).
- This group includes barium (Ba²⁺), strontium (Sr²⁺), and calcium (Ca²⁺).
- Various tests and reagents identify these cations definitively.
General Notes
- Specific colors and types of precipitates are indicators for particular cations in the scheme.
- Confirmation tests are crucial to ensure accurate identification of the cations in solution.
- Steps are designed to isolate and identify cations within specific groups.
- Negative results (no precipitate) are also essential information and sometimes lead to identifying a cation as not being in a particular group.
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Description
This lab focuses on a scheme for identifying cations in a solution through various steps and reagents. It details the use of hydrochloric acid and hydrogen sulfide to precipitate different cations and confirms their presence with further tests. Join the quiz to test your understanding of this cation identification process.
