8 Questions
Which of the following is NOT a method for determining the end point in a precipitation reaction?
Use of pH indicators
What color change signifies the end point when using ferric ammonium sulphate as an indicator?
Red
EDTA is primarily used in complexation reactions to achieve what?
To form water soluble stable complexes
Which ion determination method was used before the advent of EDTA in analytical chemistry?
Gravimetric method
Which of the following statements about oxidation and reduction is FALSE?
Oxidation is performed by oxidizing agents
What role does an adsorption indicator like dichlorofluorescein (DCF) play in analytical chemistry?
Used to detect the appearance of a complex
In a redox reaction, the reactant that gains electrons is known as the ___?
Oxidizing agent
What does the term 'chelate' refer to in the context of complexation?
A metal ion combined with two or more electron donating groups
Study Notes
Precipitation
- Precipitation reactions form relatively insoluble substances or precipitates
- Reactions must go to completion to be considered quantitative
Determination of End Point
- End point is marked by the cessation of precipitation or the appearance of turbidity
- Internal indicators are used to detect the end point
- Instrumental methods, such as Potentiometric or Amperometric, are also used to determine the end point
Indicators for Volumetric Precipitation
- Ferric ammonium sulphate indicator appears as a red color
- Potassium chromate indicator forms a red precipitate
- Adsorption indicators, such as Dichloroflurescein (DCF), Eosin Y, and Tetrabromophenolphthal ein ethyl ester, are used
Complexation
- Complexation is a quantitative analysis method for inorganic products containing metal ions, such as Al, Bi, Ca, Mg, and Zn
- Originally performed using gravimetric methods, but now uses EDTA for volumetric method
- Metal ion indicators are used, similar to pH indicators in acid-base titrations
Key Terms
- Complex: a molecule where a metal ion combines with a molecule that can donate electrons
- Chelate: a molecule with two or more groups that donate electrons
- EDTA: reacts with metal ions to form water-soluble stable complexes or chelates
Redox
- Oxidation: losing electrons, and the reactant is a reducing agent
- Reduction: gaining electrons, and the reactant is an oxidizing agent
- Electrons are transferred from one reactant to another in oxidation/reduction reactions
Learn about precipitation reactions, determining the end point of a reaction, and indicators used in volumetric precipitation in analytical chemistry.
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