Seminar 3 Theoretical part

Transcription

1 Seminar 3 Theoretical part 1. Methods of qualitative analysis inorganic In order to simplify inorganic qualitative analysis, to separate and identificate the ions of a mixture, all were divided into 5 ion groups. Figure 1 shows one common scheme for classifying into groups. General approach begins with identifying present in our solution, belonging to particular groups step by step. Investigated mixture is treated with a solution that forms precipitates with certain groups of ions and leaves the other ions undisturbed in solution. Next, precipitated ions are separated by filtration. All undisturbed ions left in the solution are treated with another solution that precipitates a different group of ions. These mechanisms are carried out until the original mixture is not separated into specific ion groups. Solutions precipitating certain groups of ions are, respectively: I. diluted HCl solution (2M HCl) II. H2S solution in the presence of diluted HCl III. (NH4)2 S solution in the presence of NH3 H2 and NH4Cl IV. diluted (NH4)2C3 solution in the presence of NH3 H2 and NH4Cl After separating all the precipitates, the ion group 5 remains in solution, since it is not precipitated by any of above solutions. Ion group 1 (in chlorides): Ag +, Hg2, Pb Ion group 2 (acid in sulfides): Hg, Pb, Cu, Cd, Sn, As 3+, Bi 3+, Sb 3+ Ion group 3 (base in sulfides and hydroxides): Fe 3+, Fe, Zn, Ni, Mn, Co (as sulfides) and Al 3+ and Cr 3+ (as hydroxides) Ion group 4 (in carbonates): Sr, Ba, Ca Ion group 5: Mg, Na +, K + and NH4 + 1

2 1 2 Ag +,Hg 2,Pb Cu,Cd,As 3+ Sn,Sb 3+,Bi 3+ Hg,Pb 2 M HCl Ion Group 2,3,4,5 H 2 S in the presence of HCl Ion Group 3,4,5 (NH 4 ) 2 S in the presence of NH 3. H 2 and NH 4 Cl Ion Group 4,5 (NH 4 ) 2 C 3 in the presence of NH 3. H 2 and NH 4 Cl Ion Group 5 Mg, Na +, K +, NH Zn,Mn,Ni Fe,Fe 3+,Co Al 3+,Cr 3+ Sr,Ca,Ba Mg,Na +, K +,NH 4 + Ion group 1 In chlorides AgCl, Hg 2 Cl 2 PbCl 2 Ion group 2 Acid-in sulfides CuS, CdS, HgS,As 2 Sb 2, Bi 2 SnS, PbS Ion group 3 Base-in sulfides and hydroxides ZnS, MnS, NiS,FeS Fe 2,CoS, Al(H) 3 Ion group 4 In carbonates SrC 3 CaC 3 BaC 3 Cr(H) 3 Figure 1. A qualitative analysis scheme for separating into ion groups. 2

3 2. Tests for functional group of organic compounds. 3

4 Problems for Seminar 3 1. Complete missing ions and coefficients: Ba +... BaS 4 Ag AgCl Na 2 C NaCl H H - Fe(H) 3 + H - Fe(H)3 Pb + Cl H - Mg(H)2 + CaC3 Fe + FeC3 + Br - AgBr Ag + I -. 4

5 2. What reagents can you use in order to detect the presence of Ca ion in a solution? (write 2 reactions) 3. Write characteristic reactions for detection of S4 ion ( 2 reactions). 4. Which compounds form cis-trans isomers? 5. How many isomers of 2,3-dihyroxybuthane and tartaric acid exist? Identify the pairs of enantiomers, diastereoisomers, meso forms. 6. How many stereogenic centers does each molecule have? 7. How many stereogenic centers does each molecule have? 8. Identify functional groups characteristic for the structure of the compound. H CH 3 C CH 3 CH CH 2 CH 2 C CH H NH 2 9. Which organic compound can be detected with use of: a) KMn4 b) Tollens reagent c) FeCl3 d) Cu(H)2 without heating or after heating 10. What reagents do you use to detect phenol? 11. What kind of particularly useful tests could you make to confirm the presence of a carbon-carbon double bound? Give an example of it. 12. What is Tollens reaction? What functional groups can be detected by using it? Give an example of it. 13. What reagents do you use to detect the carboxyl group? Give an example of it. 14. How can you distinguish HCH from CH3CH. CH 2 5

6 15. Which acids can be detected with use of NaHC3 solution? 16. What is reaction of esterification? Give an example of it. 17. Which of the below compounds can be detected with use of the iodoform reaction. H 3 C C CH 3 CH 3 CH 2 H CH 3 H CH 3 CH 2 C CH 2 CH 3 CH 3 CH H 6

7 ELECTRLYTES Formulas, ionic charge and names for some common ions Common Cations Common Anions Formula Charge Name Formula Charge Name Li + Na + K + NH4 + Ag + Mg Ca Ba Cd Zn Cu Hg2 Hg Mn Co Ni Pb Sn Fe Fe 3+ Al 3+ Cr 3+ H lithium ion sodium ion potassium ion ammonium ion silver ion magnesium ion calcium ion barium ion cadmium ion zinc ion copper(ii) ion or cupric ion mercury(i) ion or mercurous ion mercury(ii) ion or mercuric ion manganese(ii) ion or manganous ion cobalt(ii) ion or cobaltous ion nickel(ii) ion or nickelous ion lead(ii) ion or plumbous ion tin(ii) ion or stannous ion iron(ii) ion or ferrous ion iron(iii) ion or ferric ion aluminium ion chromium(iii) ion or chromic ion hydrogen ion F - Cl - Br - I - H - CN - CI - CI2 - CI3 - CI4 - CH3C - Mn4 - N2 - N3 - SCN - S HS3 - S3 HS3 - S4 HC3 - C3 Cr4 Cr27 P4 3- As fluoride ion chloride ion bromide ion iodide ion hydroxide ion cyanide ion hypochlorite ion chloride ion chlorade ion perchlorate ion acetate ion permanganate ion nitrite ion nitrate ion thiocyanate ion oxide ion sulfide ion hydrogen sulfide ion or bisulfite ion sulfite ion hydrogen sulfate ion or bisulfate ion sulfate ion hydrogen carbonate or bicarbonate ion carbonate ion chromate ion dichromate ion phosphate ion arsenate ion 7