Semi Microanalisis Quimico Cualitativo - Free ebook download as PDF File .pdf) or read book online for free. Title, Quimica analitica. I, Analisis cualitativo. Authors, F. P. Treadwell, William T. Hall. Translated by, Anselmo Ortiz Vázquez. Publisher, Uteha, near-field analysis; - por carhono 14 m Fis rad, geol carhon- 14 analysis; - de m agua, quimica qualitative analysis; - cuantitativo m agla, quimica quantitative.
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Quimica analitica. I, Analisis cualitativo - F. P. Treadwell, William T. Hall - Google книги
Therefore, the teacher should argue that s can be obtained by the square root of Kps see table what corresponds to 7,1 x mol. L-1 and 1,4 x mol. For such salt, mol.
The teacher should ask the students what salt precipitates first, on the basis of molar solubility data. After some calculations, the role of the smaller s can be discussed.
This acid was slowly added until pH 3 the students should measure the pH. Along the acid addition, an effervescence will be observed. Moreover, part of the initial precipitate will dissolve. As expected, a yellow precipitate will remain in the test tube, since the BaCrO4 is insoluble in dilute acetic acid Vogel, At his point, for teaching aims, carbonate and phosphate speciation diagrams Figure analysis cualitativo quimica and 3, respectively analysis cualitativo quimica be discussed.
These diagrams represent the molar fraction of each species at different pH. The discussion should be focused on which species would be present in the pH of the solution after acetic acid addition pH 3.
Carbonate speciation diagrams Gutz, Figure 3. Phosphate speciation diagrams Gutz, Indeed, the diagram shows that CO2 is the unique compound at pH close to 3. Clearly, the acetic acid addition eliminates all CO anions from the mixture, what is attested by the effervescence.
The Ba3 PO4 2 is soluble in acid media what can analysis cualitativo quimica understood on the basis of analysis cualitativo quimica phosphate diagram Figure 3.
Thus, the students are encouraged to investigate which species are present in each phase of the solution: Furthermore, the teacher should request that students whrite the equation for the decomposition of carbonic acid 4 and the equation related to the Ba3 PO4 2 solubilization 5. According to the proposed experimental procedure, the supernatant containing the H3PO4 and H2PO4- should be transferred to the test tube B.
The BaCr2O4 will remain in the test tube A. Analysis cualitativo quimica such procedure will be observed the formation of a partially soluble white solid. analysis cualitativo quimica
Analisis cualitativo y quimica inorganica.
At this point, the teacher should ask some questions related to the speciation diagram for instance, what is the predominant species at pH 5?
Once the predominant species is found, what is the composition analysis cualitativo quimica the salt formed?
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Would you analysis cualitativo quimica able to write the equation for the PO characterization reaction? At pH values near 5, the predominant ion is the dihydrogen phosphate H2PO Thus, the sodium dihydrogen phosphate NaH2PO4 will be the obtained salt according to equation 6. In the presence of dilute mineral acids, such as HCl, the BaCrO4 is fully soluble and a yellow solution of chromate CrO becomes orange-red due to conversion these analysis cualitativo quimica in dichromate ions Cr2O Vogel, For his particular distribution, the discussion should be slightly more rigorous.
The diagram for the Cr VI species is depicted in Figure 4. Such diagram should be discussed with the students.
The chromate speciation diagram in Figure 4 allows a rigorous discussion. The teacher should ask at first, about the predominant ion at this pH.
According to the Figure 4 this solution contains several species in equilibrium, that can be discussed based analysis cualitativo quimica the equations 7 and 8 Kalbus, et al. The predominant color of the solution depends on the particular ion concentration.