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FE Review Chemistry Heather J. Shipley Assistant Professor Civil and Environmental Engineering UTSA Basic Concepts Nucleus of atom Proton: positively charged particle, 1.00728 amu Neutron: neutral particle, 1.00866 amu Electron: negatively charged particle, 0.0005486 amu neutron proton electron Definitions • Atomic mass: the total mass of protons, neutrons, and electrons in a single atom • Atomic number: the number of protons in the nucleus • Element: a substance only composed of one type of atom • Isotope: element with the same number of protons but different atomic masses Electron Configuration Periodic Trends Electronegativity Ionization Energy Atomic Radius • Electronegativity: is a chemical property that describes the tendency of an atom or a functional group to attract electrons (or electron density) towards itself. • Ionization energy: is the energy required to remove electrons from atoms or ions. • Atomic radius: the size of the atom Molecular Bonding E.g. CaCl2 = 40.08+2(35.45) = 110.97 g/mole Elements combine to form molecules in order to fill their shells. Usually an element has 8 electrons around it, except H which is 2 and B which is 6 Formed by sharing a pair of electrons formed by electrostatic attraction between positive and negative ions Gas Laws • Ideal Gas law – PV= nRT • No intermolecular forces • Gas molecules occupy no specific volume • Standard Temperature and Pressure – 0°C and 1atm – 22.4L/mole Gas Laws cont. – P = Pa +Pb +Pc+… • Henry’s Law: relates gases and solutions – KH=Pgas/C = partial pressure of a gas (atm)/ concentration in solution (M) Solution Chemistry Solution Chemistry Equilibrium aA + bB = cC +dD • K = [C]c[D]d/ [A]a[B]b = products/reactants pH • Water dissociates into H+ and OH– H2O = H+ + OH- • Equilibrium – Kw = [H+][OH-]/[H2O] = [H+][OH-] • Kw = 1x10-14 • pH = log(1/[H+]) – pH >7: alkaline ([OH-]>[H+]) – pH < 7: acidic ([OH-]<[H+]) • pOH = log(1/[OH-]) • pH+pOH = 14 Example • Calculate the pH of 10g/L NaOH solution – [NaOH] = 10g/L*1mol/40g = 0.25M – [OH-] = 0.25M * 1mol OH/1mol NaOH = 0.25M – pOH = log(1/0.25) = 0.602 – pH = 14-0.602 = 13.398 Chemical reactions • In chemical reactions elements or molecules rearrange themselves to form more stable molecules. The reaction is highly favored if electrons are transferred from an element which loosely binds electrons to an element that tightly binds electrons. The element which donates the electrons is the reducing agent and the element which receives is the oxidizing agent. Reactions • Precipitation/Dissolution Reactions – Dissolved ions react with other ions to form insoluble compounds – AaBb (s) = aAb+ + bBa– Ksp = [A]a[B]b • Undersaturated if [A]a[B]b < Ksp • Saturated if [A]a[B]b = Ksp • Super-saturated if [A]a[B]b > Ksp • Acid/Base reactions – Substances that influence pH, see earlier slides • Complexation Reaction – Occurs when 2 or more atoms, molecules, or ions combine and form a stable product • E.g. Fe(H2O)62+ Reactions • Oxidation and Reduction Reactions (Redox) – Involves transfer of e-; one compound gives up e- the other takes them up – Compound giving up e- is being oxidized, so reducing agent – Compound accepting e- is being reduced, oxidizing agent • Ex. Corrosion of Fe – Fe0 = Fe2+ +2e– 2H+ + 2e- = H2 (g) – Overall Fe0 + 2H+= Fe2+ +H2 (g) • Combustion Reaction: burning of fuel with oxygen Electrochemical cells Balancing Equations • 2 rules – Mass must be conserved • The number of atoms of an element on the left hand side of the rxn needs to equal the amount on the right • The atoms can change what they associate with but not be created or destroyed – Charge must be conserved • charge on the left must equal the charge on the right Kinetics • Speed of a reaction • Zero order: rxn proceeds at a rate independent of the conc. of any reactant – C-C0 = -kt • First Order: rxn proceeds at a rate directly proportional to the concentration of one reactant – C = C0e-kt – Half life • t1/2 = ln2 / k • Second order: proceeds at a rate proportional to the square of the conc. of 1 reactant or the product of 2 reactants – 1/C-1/C0 = kt Organic Chemistry • Alkanes Organic Chemistry