L e c t u r e 1

1. Lecture1 Analytical chemistry. Chemical analysis.Calculation of рН. Associate prof. L.V. Vronska Associate prof . M.M. Mykhalkiv

2. Outline Object and task of analytical chemistry. Chemical analysis and its varieties. The importance of analytical chemistry in Pharmacy. Methods of analysis, their classification. Main principles in the theory of strong electrolytes. The Law of Mass Action in analytical chemistry. Main types of chemical equilibrium, which are utilized in analytical chemistry. Bronsted-Lowry theory of acids and bases. Calculation of рН and рОН aqueous solutions of acid and base. Calculation of рН solutions of ampholytes. Calculation of рН solutions of salts. Calculation of рН of buffer solutions. Acid-base equilibrium in nonaqueous solvents.

3. 1. Object and task of analytical chemistry. Chemical analysis and its varieties. The importance of analytical chemistry in Pharmacy. Methods of analysis, their classification. Analytical chemistry – a sub-discipline of Chemistry about methods of the analysis or methods of reception of the information about elementary objects.

4. Analytical chemistry a sub-discipline of Chemistry which develops theoretical basis and methods of the chemical analysis. Object of analytical chemistry is to define chemical compounds in substances.

5. Main divisions of Analytical Chemistry: The qualitative analysis: fractional and systematic methods The quantitative analysis: 1. chemical methods 2. instrumental methods: physical methods of analysis physical-chemical methods of analysis

6. Mixture of components I, J, K, L, M groups Components I  M Components I  M Components I  M Components I  M Components I  M Component I Components J M Component L Components I, J, K, M Component J Components I, K, L, M Scheme of Fractional Analysis of Complex Mixtures Aliquots identical mixtures Reagent F Reagent W Reagent Q

7. Scheme of Systematic Path of Complex Mixture Analysis Mixture of substances of I, J, K, M group Group I Components I1, I2, I3 … Mixture of substances of groups J … M Mixture of substances of groups K, M Group J Components J1, J2, J3 … Reagent A Reagent B

8. Scheme of Analysis of Group J Components J1, J2, J3, J4, J5 Components J1, J2 Components J3, J4,J5 Component J3 Component J1 Component J2 Components J4, J5 Component J4 Component J5 Reagent N Reagent Y Reagent Z Reagent T

10. The main goal of the qualitative analysis is searching of elements, ions or chemical compounds that are contained in the investigated substance. The main goal of the quantitative analysis is to define the quantity of the mixture ratio or percentage of elements (ions) in substance.

11. Reactions in analytical chemistry Specific Selective Specific reactions give an analytical effect only with one individual substance. NH4+ + OH - = NH3 + H2O. Selective reactions give identical or similar analytical effects with small number of ions (2-5). HCl: Pb2+ + 2Cl- =PbCl2↓ Ag+ + Cl- =AgCl ↓ Hg22+ + 2Cl- =Hg2Cl2 ↓

12. The group reagent is the reagent which will meet the following requirements: • It should precipitate cations virtually, quantitatively (concentration of cations in a solution should be less than 10-6 M); • The precipitate should be easily dissolved in certain reagents; • Excess reagent should not alter determination of those ions which remain in solution.

13. Tasks of analytical chemistry: Research methods of qualitative and quantitative analysis of Nb, Ta, Zr, Ti, Hf, Mo, W, rare-earth andother elements in mixture, because they are used in the modern techniques. Research methods for detection and definition of microquantities of elements, because often physical and chemical properties of materials are predetermined by their presence.

14. Detect and Define chemical elements and substances in the environment: soil, air, water, plants Investigate the complex influence of related substances on a life of plants, animals and people.

15. The Importance of analytical chemistry in Pharmacy. Synthesis of drugs (synthetic or natural) is necessarily supervised by methods of analytical chemistry. Definition of period of drugs validity is based on methods of analytical chemistry.

16. Chemical analysis and its varieties: Elemental analysis Function analysis Molecular analysis Phase analysis Diffraction analysis

17. Elemental analysis is qualitative and quantitativeanalysis of elements in compound clear substance

18. Function analysis is the analysis which answer what functional groups are contained in investigated substance Methods of the molecular analysis receive the information about substances which consist of molecules or formular parts.

19. Phase analysis – detection and definition of different phases (solid, liquid, gas), which are contained in the investigated system. Diffraction analysisdetermines the crystal lattice structure containing atoms, molecules and ions.

20. Pharmaceutical analysis is determination of drug quality (manufactured or pharmacy compounded) Pharmaceutical analysis includes: analysis of drugs analysis of medicinal herbs process monitoring of drugs toxicological analysis judicial-chemical analysis

21. IUPAC Classification of analytical methods in accordance with mass and volume of analytic sample

23. The signal which bears the information on elementary objects, is called as an analytical signal.The analytical signal can be the carrier for both qualitative and quantitative information. Sensitivity of analytical reaction is the least amount of substance, which can be detected with the reagent in one drop of solution.

24. The sensitivity express to next correlated values: Limit of detection = Determined minimum (m) – the least amount of substance, which present in analysed solution and can be detected with the reagent. Calculated in g. 1 g = 0,000001 g. Limit of concentration = Minimal concentration (Cmin) – the least concentration of substance in the solution which still can be detected in small portion or volume of analysed solution.

25. Maximum of dilution (W = 1/Cmin) – quantity (ml) of solution, containing 1 g of the analysed substance, which can be detected with a definite reaction (reagent). Analytical reaction is considered more sensitive under conditions when determined minimum and minimal concentration of analyzed solution are low and maximum of dilution is high.

26. 2. Main principles of theory of strong electrolytes. activity(а) –effective concentrationof ions in solution, when it reacts

27. To calculate activity coefficients use the following: 1.Ionic strength of solution where ci and zi are the concentration and charge of the ith ion. 2.Activity coefficients for ionic solutes, depend on the ionic strength of solution by using the extended Debye–Hückel theory

28. To calculate activity coefficients use the Debye–Hückel equation if 0,01 if 0,1 if 1,0

29. Experimentally is possible to find only the Mean activity coefficient: for binary electrolyte AB for electrolyte structure AmBn

30. Mean activity coefficient may be calculated theoretically by using Debye–Hückel equation: if 0,01 if 0,1 if1,0.

31. For simplification of calculations of activity coefficients use these assumptions: 1. Activity coefficients of ions with identical charge irrespective of ion’s radius are approximately equal. 2. Activity coefficients of neutral parts in dilute solutions of electrolytes equals 1. 3. Very dilute solutions of electrolytes are possible to consider ideal.

32. 3. The Law of Mass Action in Analytical Chemistry. Concentrational (real) constantof chemicalequilibrium nA + mB  lC +pD p-functionof constantequilibrium pK = –lgK.

33. КТ – thermodynamicequilibriumconstant(it depends on temperature and pressure) where f – activity coefficient We use KR, when we have real conditions (influence of ionic strength, temperature and pressure)

34. КC – conditionalequilibrium constant where C – formality, is a substance’s total concentration in solution regardless of its specific chemical form. where  - parts per mol

35. We use KC, when we have the following real conditions (influence of ionic strength, temperature and pressure, competitive reactions)

36. Mass balance equation, which is simply a statement of the conservation of matter. In a solution of a monoprotic weak acid (base), for example, the combined concentrations of the conjugate weak acid (base), HA, and the conjugate weak base (acid), A–, must equal the weak acid’s (base’s) initial concentration, CHA. H2S  H+ + HS- HS- H+ + S2- CS = [S2–] + [HS–] + [H2S].

37. A charge balance equation is a statement of solution electroneutrality. Total positive charge from cations = total negative charge from anions Mathematically, the charge balance expression is expressed as where [Mz+]iand [Az–]jare, respectively, the concentrations of the ith cation and the jth anion, and (z+)i and (z–)j are the charges of the ith cation and the jth anion. The charge balance equation for an aqueous solution of Ca(NO3)2 is 2 [Ca2+] + [H3O+] = [OH–] + [NO3–]

38. Main types of chemical reactions which are used in analytical chemistry: Acid-base reaction(the reaction of an acid with a base) CH3COOH(aq) + NH3(aq) CH3COO–(aq) + NH4+(aq) A precipitation reaction occurs when two or more soluble species combine to form an insoluble product. Pb2+(aq) + 2Cl–(aq) PbCl2(s)

39. reaction between the metal ion and the ligand is typical of a complexation reaction. Cd2+(aq) + 4(:NH3)(aq) Cd(:NH3)42+(aq) redox reaction - an electron-transfer reaction. 2Fe3+(aq) + H2C2O4(aq) + 2H2O(l) 2Fe2+(aq) + 2CO2(g) + 2H3O+(aq)

41. 4. Bronsted-Lowry theory of acids and bases. A substance, that dissolves in water to give an electrically conducting solution is called an electrolyte. A substance, that dissolves in water to give nonconducting or very poorly conducting solution is called a nonelectrolyte.

42. According to Svante Arrhenius concept: Acid is any substance that, when dissolved in water, increase the concentration of hydrogen ion H+. Base is any substance that, when dissolved in water, increase the concentration of hydroxide ion OH–. NaOH  Na+ + OH– HCl  H+ + Cl–

43. A useful definition of acids and bases was indepen-dently introduced by Johannes Brønsted (1879–1947) and Thomas Lowry (1874–1936) in 1923. acidsare proton donors basesare proton acceptors Acid  Base + Н+

44. Constant reaction of a dissociationsolventhas equation Autoprotolysisconstantof solvent is product of activity lyonium and lyate

45. Neutrality of solution determines activity of lyonium and lyate іons: Condition of neutrality

46. рН of some solvents

47. TheBrønsted-Lowry concept of acids and bases has greater scope than the Arrhenius concept: the general description of acid-base reaction possibility a quantitative estimation strength of acid and base НА + Н2О  Н3О+ + А– B + H2O  BH+ + OH–

48. Solvents: progenic (A species that can serve as a proton donor) protophilic (A species that can serve as a proton acceptor) amphiprotic (A species that can serve as both a proton donor and a proton acceptor) aprotic(A species that can’t serve a proton)

49. proton acceptor’s properties increase  H2SO4; CCl3COOH; CH3COOH; H2O; C2H5OH; NH3; C5H5N proton donor’s properties increase 

50. 5. Calculation of рН and рОН aqueous solutions of acid and base. • Calculation of рН and рОН of strong acid’s and base’s solutions. pH + pOH=14 • For dilute solutions of strong acid and base (if C110-4M):