Podcast
Questions and Answers
When reacting Al(OH)3 with NaOH and H2O2, the ______ will dissolve while the ppt of Fe(OH)3 will not be dissolved.
When reacting Al(OH)3 with NaOH and H2O2, the ______ will dissolve while the ppt of Fe(OH)3 will not be dissolved.
ppt of Al(OH)3 and Cr(OH)3
In the test for Fe+3, adding NH4SCN results in a ______ color.
In the test for Fe+3, adding NH4SCN results in a ______ color.
blood red
The yellow ppt formed when testing for Cr+3 occurs after adding ______ until acidity.
The yellow ppt formed when testing for Cr+3 occurs after adding ______ until acidity.
diluted acetic acid
When testing for Al+3, a white gelatinous ______ is produced after adding NH4Cl and boiling.
When testing for Al+3, a white gelatinous ______ is produced after adding NH4Cl and boiling.
The ppt of Fe(OH)3 formed during the reactions appears as ______ in color.
The ppt of Fe(OH)3 formed during the reactions appears as ______ in color.
A cation is a positive charge ______.
A cation is a positive charge ______.
Group II A cations include ______, Hg, Cd, and Bi.
Group II A cations include ______, Hg, Cd, and Bi.
The precipitating reagent for Group II A cations is ______ + H2S.
The precipitating reagent for Group II A cations is ______ + H2S.
Canary yellow ppt indicates the presence of ______ in Group II A cations.
Canary yellow ppt indicates the presence of ______ in Group II A cations.
The brown ppt observed belongs to ______ in Group II A cations.
The brown ppt observed belongs to ______ in Group II A cations.
Black ppt indicates the presence of ______ or Cu+2.
Black ppt indicates the presence of ______ or Cu+2.
To identify the cations, one may use dil. ______ and dil. H2SO4.
To identify the cations, one may use dil. ______ and dil. H2SO4.
Cations from Group III include Al+3, Fe+3, and ______.
Cations from Group III include Al+3, Fe+3, and ______.
1ml c.HCl + 2dps H2O2 will yield the ______
1ml c.HCl + 2dps H2O2 will yield the ______
If a white ppt is formed, it indicates the presence of ______
If a white ppt is formed, it indicates the presence of ______
The reagent used to precipitate group III cations is ______ OH.
The reagent used to precipitate group III cations is ______ OH.
From the solution containing Cu+2, a ______ solution is observed.
From the solution containing Cu+2, a ______ solution is observed.
To identify Cd+2, the solution must be combined with ______ acid and 1 dp K-ferrocyanide.
To identify Cd+2, the solution must be combined with ______ acid and 1 dp K-ferrocyanide.
When testing for Cr+3, a ______ precipitate is formed.
When testing for Cr+3, a ______ precipitate is formed.
If the solution does not dissolve after heating, ______ HCl should be added dropwise.
If the solution does not dissolve after heating, ______ HCl should be added dropwise.
The mixture of group III cations includes Fe+3, Cr+3, and ______.
The mixture of group III cations includes Fe+3, Cr+3, and ______.
Flashcards
Cation
Cation
A positively charged ion, represented by a symbol with a superscript plus sign.
Precipitating reagent
Precipitating reagent
A chemical that reacts with specific cations to form an insoluble precipitate, allowing for their separation and identification.
Precipitate
Precipitate
A solid, insoluble substance that forms during a chemical reaction, often used to identify specific ions.
Centrifugation
Centrifugation
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Group analysis
Group analysis
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Scheme for identification
Scheme for identification
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Soluble
Soluble
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Insoluble
Insoluble
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Al(OH)₃ precipitate
Al(OH)₃ precipitate
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Fe(OH)₃ precipitate
Fe(OH)₃ precipitate
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Separation of Fe(OH)₃
Separation of Fe(OH)₃
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Fe³⁺ test with NH₄SCN
Fe³⁺ test with NH₄SCN
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Al³⁺ test with NH₄Cl
Al³⁺ test with NH₄Cl
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Hg+2 Identification in Group II Cations
Hg+2 Identification in Group II Cations
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Soluble Group II Cations
Soluble Group II Cations
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Bismuth (Bi+3) Identification
Bismuth (Bi+3) Identification
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Soluble Cations after NH3 Treatment
Soluble Cations after NH3 Treatment
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Cadmium (Cd+2) Identification
Cadmium (Cd+2) Identification
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Copper (Cu+2) Identification
Copper (Cu+2) Identification
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Group III Cations List
Group III Cations List
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Group III Precipitating Reagent
Group III Precipitating Reagent
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Study Notes
Cations (Group IIA and Group III)
- Cations are positively charged ions. Represented as X⁺.
- Cations are classified into six groups based on the precipitating reagent used.
Group IIA Cations (Cu²⁺, Hg²⁺, Cd²⁺, Bi³⁺)
- The precipitating reagent is 0.25N HCl + H₂S.
- If a powder is not easily dissolved/ mixed with water, add concentrated HCl dropwise until it dissolves.
- Add an excess of H₂S to the mixture to create an insoluble precipitate.
- The resulting precipitate is analyzed for the presence of specific cations. This includes:
- Canary yellow ppt → Cd²⁺
- Brown ppt → Bi³⁺
- Black ppt → Hg²⁺, Cu²⁺
- A further test, using HNO₃, H₂SO₄ and hydrogen peroxide (H₂O₂) with concentrated HCl will distinguish the specific cation.
Group III Cations (Fe³⁺, Cr³⁺, Al³⁺)
- The precipitating reagent is NH₄OH (NH₃) + 10% NH₄Cl.
- Add concentrated HCl dropwise to the powder if it does not initially dissolve with water.
- Add NH₄Cl + NH₃ until the mixture becomes alkaline
- The resulting precipitate is further analyzed using different reagents:
- White gelatinous ppt → Al(OH)₃
- Reddish brown ppt → Fe(OH)₃
- Gray ppt → Cr(OH)₃
- If further analysis reveals a dissolved solution, further testing will differentiate between Al³⁺, Cr³⁺ and Fe³⁺ ions.
Centrifugation
- Centrifugation is a process used to separate particles of different densities in a mixture.
- Centrifuges spin at high speeds, causing heavier particles to settle to the bottom of the tube, creating a pellet.
- Lighter particles remain suspended above the pellet, which can be separated as a supernatant.
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