Download FE Review Chemistry - UTSA College of Engineering

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