Titulação de complexação: diferenças entre revisões
Conteúdo apagado Conteúdo adicionado
Linha 25:
:M<sup>2+</sup> + H<sub>4</sub>Y → MH<sub>2</sub>Y + 2H<sup>+</sup>
tenda para a direita.
tenda para a direita. Carrying out the reaction in a basic buffer solution removes H<sup>+</sup> as it is formed, which also favors the formation of the EDTA-metal cation complex reaction product. For most purposes it can be considered that the formation of the metal cation-EDTA complex goes to completion, and this is chiefly why EDTA is used in titrations / standardizations of this type.▼
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To carry out metal cation titrations using EDTA it is almost always necessary to use a [[complexometric indicator]], usually an organic [[dye]] such as [[Fast Sulphon Black]], [[Eriochrome Black T]], [[Eriochrome Red B]] or [[Murexide]], to determine when the end point has been reached. These dyes bind to the metal cations in solution to form colored complexes. However, since EDTA binds to metal cations much more strongly than does the dye used as an indicator the EDTA will displace the dye from the metal cations as it is added to the solution of analyte. A color change in the solution being titrated indicates that all of the dye has been displaced from the metal cations in solution, and that the endpoint has been reached.
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