PCQA 111 Week 7: Acids and Bases, Chemical Kinetics, and Equilibrium PDF

OUR LADY OF FATIMA UNIVERSITY College of Pharmacy PHARMACEUTICAL INORGANIC CHEMISTRY WITH QUALITATIVE ANALYSIS (PCQA 111) WEEK 7: ACID AND BASES UNIT OUTLINE: ▷Acids and Bases ▷Chemical kinetics ▷ Chemical equilibrium 2 ARRHENIUS THEORY (1884) In water solutions….....

OUR LADY OF FATIMA UNIVERSITY College of Pharmacy PHARMACEUTICAL INORGANIC CHEMISTRY WITH QUALITATIVE ANALYSIS (PCQA 111) WEEK 7: ACID AND BASES UNIT OUTLINE: ▷Acids and Bases ▷Chemical kinetics ▷ Chemical equilibrium 2 ARRHENIUS THEORY (1884) In water solutions….. ○ Acid – yields H(1+) and H3O (1+) ions ○ Base – yields OH (1-) ions Not applicable for non-aqueous solvents 3 BRONSTED-LOWRY THEORY (1923) Acid – Donates proton H(1+) Base – Accepts proton A  H(+) + B ACID BASE 4 BRONSTED-LOWRY THEORY Acid – Donates proton H(1+) Base – Accepts proton 5 BRONSTED-LOWRY THEORY HCl + H2O  Cl(1-) + H3O(1+) Hydronium/Oxonium ion is always formed when an acid dissolves in water. It may also be written as H(1+) alone, though practically it is nonexistent in solution. NH3 + H2O  NH4(1+) + OH(1-) 6 LEWIS THEORY (1923) Acid – accepts electron pair Base – donates electron pair To form coordinate covalent bonds 7 LEWIS THEORY Acid – accepts electron pair Base – donates electron pair 8 Theories on Acids and Bases 9 pH and pOH pH = -log[H3O+] pOH = -log[OH-] Since that [H3O+][OH-] = Kw, it follows that pH + pOH = pKw = 14 For neutral solutions where both [H3O+] and [OH-] are equal to 1.0 x 10^7 M pH =pOH = 7.0 10 For ACIDIC SOLUTIONS [H3O+] > 1.0 x 10 ^7 M pH – less than 7.0 pOH – greater than 7.0 11 For BASIC SOLUTIONS [H3O+] < 1.0 x 10^7 M pH – greater than 7.0 pOH – less than 7.0 12 OUR LADY OF FATIMA UNIVERSITY College of Pharmacy PHARMACEUTICAL INORGANIC CHEMISTRY WITH QUALITATIVE ANALYSIS (PCQA 111) WEEK 7: CHEMICAL KINETICS AND EQUILIBRIUM CHEMICAL KINETICS Is the discipline that is concerned with the mechanism by which a chemical process gets to its final state from its initial state and the rate in which this reaction proceeds. Is the study of reaction rates and the mechanism or step sequence under which reactions occur. 14 CHEMICAL KINETICS 1. Study the rate of chemical change. 2. The way this rate is influenced by factors. 15 Rate of Reaction Is the amount of chemical change, which takes in given interval of time. Measured in terms of products formed/ lost per unit time at a given temperature 16 Rate of Reaction Few chemical reactions occur in a single step. There are usually one or more intermediate products, which form and the stepwise sequence of reactions is known as the reaction mechanism. 17 Molecular Collision Theory A chemical change takes place as a result of collision of molecules. The greater the number of collision per unit time, the greater the conversion of initial substances into products per unit time that is, the greater the speed of reaction. However, not all collisions of molecules necessarily result in chemical change. 18 Molecular Collision Theory 1. Before molecules can react, they must possess a certain minimum energy termed activation energy. Only molecules with the necessary activation energy will undergo reaction. 2. The orientation of the colliding molecules must be favorable for the making and breaking bonds. 19 Molecular Collision Theory 20 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Nature of the reacting substances ○ Substances differ in activity and hence in the speed with which they react with other substances. 21 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Nature of the reacting substances ○ The active metals displace hydrogen vigorously and rapidly from acids. ○ The less active metabolites act slowly, if at all. ○ Metals differ in their rates of corrosion because of differences in speed of combination with oxygen and other elements. 22 23 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Temperature ○ Reacting molecules or atoms must collide before they can react. ○ High temperature  molecules or atoms move faster and come in contact more often (at gaseous state) 24 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Temperature ○ In general, the speed of a chemical change or tripled for every 10 degrees Celsius increase in temperature regardless of whether the reactions is exothermic or endothermic. 25 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Temperature 26 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Catalysts ○ Is a substance that alters the rate of a chemical reaction without being used up in the reaction. The catalyst may be recovered unchanged at the conclusion of the process. 1. Accelerators (+) 2. Inhibitors (-) 27 FACTORS WHICH INFLUENCE THE SPEED OF CHEMICAL REACTIONS Concentration ○ When concentration of a reactant is increased, more molecules are crowded into given volume and the total number into a given volume and the total number of number of molecular collisions per unit time is increased - Increase in the rate of the reaction. 28 Law of Mass Action States that the speed of a chemical change is proportional to the concentration of the reacting substances. 29 Thanks! Any questions? You can find me at: [email protected] 30