Lecture 3 - General Inorganic Chemistry PDF

Pharmaceutical Analytical Chemistry I (PC 111) Level I Students (Pharm D Clinical) General Inorganic Chemistry [Lecture 3] Dr. Galal Magdy, PhD 1  Objectives After this lecture, you should...

Pharmaceutical Analytical Chemistry I (PC 111) Level I Students (Pharm D Clinical) General Inorganic Chemistry [Lecture 3] Dr. Galal Magdy, PhD 1  Objectives After this lecture, you should know: Solution terminology. Different types of electrolytes. Acids and Bases. 2  Solution Terminology Solution: A homogenous mixture of 2 or more substances.  two or more substances in a single phase, one is the solvent and others are solutes. Solvent: the substance present in the solution in largest proportion. Solute: All other substances which present in the smaller amount(s) and dissolved in the solvent. Solute + Solvent = solution Exceptions: Conc. H2SO4; a mixture of 96%H2SO4 + 4%H2O; water is the Solvent. 3  Concentrated solution: is that solution containing relatively large proportion of solute to solvent. Diluted solution: is that solution containing smaller proportion of solute to solvent. Saturated solution: A solution in which the solvent can dissolve no more of a specific solute at a particular temperature. (This amount of solute is called the solubility of that particular solute). Unsaturated solution: is that solution containing less solute than is needed for saturation. (Q. Give name?) Example: 35.7 g of NaCl per 100 mL of water at 25°C  Saturated 20 g of NaCl per 100 mL of water at 25°C  Unsaturated 4  Q: How much NaCl is needed to saturate a solution containing 20 g/100 mL? Answer: we should add 15.7 g (15.7 + 20 = 35.7 g/100 mL). N.B: No relation between terms: Saturated or unsaturated, and the terms: concentrated or diluted. i.e. Not each saturated solution is concentrated and Not each unsaturated solution is diluted. (T or F) Ex1: Saturated solution of AgCl at room temp. = 0.000089 g AgCl/100 mL  This solution could certainly considered Diluted. EX2: Saturated solution of Lithium Chlorate = 500 g / 100 mL  This solution could certainly considered Concentrated. EX3: Unsaturated solution of Lithium Chlorate = 400 g / 100 mL  This solution could certainly considered Concentrated. 5  Supersaturated solution: is that solution containing more solute than ordinarily required for saturation. Supersaturated solutions are unstable and releases its extra-solid reaching the point of saturation when: 1. A tiny crystal (seed) of solid is added, additional solute crystallizes on this "seed" crystal. 2. Further cooling of the supersaturated solution. 6  Electrolytes and Nonelectrolyte Solutions Non-electrolyte weak electrolyte strong electrolyte 7 Nonelectrolytes: Molecular substances having no tendency to dissociate in water. Their solutions don't conduct electricity. (T or F)  Ex: Sugar and ethyl alcohol. Electrolytes:  Strong electrolytes: Substances that completely dissociated (ionized) in aqueous solution. Their solution can conduct electricity.  Ex: NaCl, HCl (Strong acids and bases) NaCl(s)  Na+(aq) + Cl-(aq) HCl(aq) + H2O  H3O+(aq) + Cl-(aq) 8  Weak electrolytes: Substances that dissociate to small extent (not completely dissociated = partially dissociated) in aqueous solution. They are weak conductive to electric current. (T or F)  Ex1: Acetic acid in water (Weak acids and bases) CH3COOH(aq) + H2O ↔ H3O+(aq) + CH3COO-(aq) CH3COOH ionizes to only 0.42% w/v.  Ex2: NH4OH, HCN  Ex3 : H2O ionizes to only 10-7 M. H2O(aq) + H2O ↔ H3O+(aq) + OH-(aq) 9  Acids and Bases Acids A compound which donates proton (H+) upon ionization (Arrhenius theory). A compound which donates proton (H+) upon ionization (Bronsted-Lowry theory). A compound that can accept a lone-pair of electrons from a base (Lewis theory). N.B. Acid  Conjugate base (anion) HCl  Cl- ( chloride) HCN  CN- (cyanide) H2S  S2- (sulphide) 10  Acids and Bases Acids  Oxoacids [HNO3 , H2SO4 , H3PO4]  Monoprotic acid: are able to furnish one H+ (HCl, HNO3).  Dioprotic acid: are able to furnish 2 H+ (H2SO4).  Triprotic acid: are able to furnish 3 H+ (H3PO4).  Acidic anhydride: acid without water (CO2 , SO2).  Acid salts: when a base reacts with polyprotic acid, two or more salts may be formed.  Examples: Salts of H2SO4 (NaHSO4,Na2SO4) and Salts of H3PO4 (Na2HPO4, NaH2PO4, Na3PO4). 11  Acids and Bases Bases  Base = alkali, alkaline = basic.  A substance that produces OH- upon ionization (Arrhenius theory).  A substance that accepts proton (H+) upon ionization (Bronsted-Lowry theory).  A substance that donates a lone-pair of electrons to form a coordination bond (Lewis theory).  Examples of bases: NaOH, KOH, NH4OH (NH3).  Basic anhydride: Metal oxides (Na2O,CaO). 12  AMPHOTERISM Amphoteric Substances: Substances that act as acid and base like some metal hydroxides. (Q. Give name?) EX1: If a solution of NaOH is added, drop by drop, to a solution of a soluble zinc salt, a white precipitate Zn(OH)2 will first form. On further addition of NaOH solution, the solid Zn(OH)2 will gradually dissolve until clear solution of [Zn(OH)4]2- is obtained. Zn(OH)2 + 2OH- → [Zn(OH)4]2- (tetrahydroxozincate complex) Zn(OH)2 will also dissolve in any strong acid Zn(OH)2 + 2H+ → Zn2+ + 2H2O EX2: Cr(OH)3 + OH- → [Cr(OH)4]- Cr(OH)3 + 3H+ → Cr3+ + 3 H2O 13  Isoelectric point: The point at which the acidic ionization and basic ionization are equal. (Q. Give name?) Analytical application of amphoteric substances: EX1: Separation of Al3+ from Fe3+ could be performed by addition of excess NaOH where Al3+ is firstly precipitated as Al(OH)3 and then it dissolves in NaOH giving soluble sodium aluminate. EX2: Zn2+ ion is separated from Mn2+ by application of the same principle. 14 15 Common chemical symbols 16 Thank You