AMUEEE Chemistry Syllabus

State Le Chatelier's principle.

If a system at equilibrium is disturbed by a change in concentration, pressure or temperature, the equilibrium shifts to counteract the change and re-establish equilibrium.

How are Kp and Kc related for a gaseous equilibrium?

Kp = Kc (RT)^(delta n), where delta n = (moles of gaseous products) - (moles of gaseous reactants).

Define pH and pOH, and state their relationship at 25 C.

pH = -log[H+] and pOH = -log[OH-]. At 25 C, pH + pOH = 14.

What is the common ion effect?

The suppression of ionization of a weak electrolyte by adding a strong electrolyte that has an ion in common with it, shifting equilibrium to reduce dissociation.

Define solubility product (Ksp) for a salt AB.

Ksp = [A+][B-], the product of the molar concentrations of the ions in a saturated solution, each raised to its stoichiometric coefficient.

State Henderson-Hasselbalch equation for a buffer.

pH = pKa + log([salt]/[acid]) for an acidic buffer (and pOH = pKb + log([salt]/[base]) for a basic buffer).

State Raoult's law for a solution of two volatile liquids.

The partial vapour pressure of each component equals its mole fraction times its pure vapour pressure: P_A = X_A.P_A(pure).

List the four colligative properties of solutions.

Relative lowering of vapour pressure, elevation of boiling point, depression of freezing point, and osmotic pressure.

Give the equation for osmotic pressure.

pi = CRT = (n/V)RT, where pi is osmotic pressure, C is molar concentration, R is gas constant, T is temperature in kelvin.

What is the van't Hoff factor (i) and what does i > 1 indicate?

i = observed colligative property / calculated value (assuming no association/dissociation). i > 1 indicates dissociation; i < 1 indicates association.

Give the Nernst equation for an electrode at 298 K.

E = E0 - (0.0591/n) log Q, where E0 is standard electrode potential, n is electrons transferred, and Q is the reaction quotient.

State Faraday's first law of electrolysis.

The mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed: m = ZIt (Z = electrochemical equivalent).

How do molar conductivity and conductivity change with dilution?

Molar conductivity increases with dilution (more ions free to move per mole), while conductivity (specific conductance) decreases with dilution due to fewer ions per unit volume.

Relate standard cell potential to Gibbs energy and to equilibrium constant.

Delta G0 = -nFE0_cell and Delta G0 = -RT ln K, so E0_cell = (RT/nF) ln K = (0.0591/n) log K at 298 K.

Write the integrated rate law for a first-order reaction and its half-life.

k = (2.303/t) log([A0]/[A]); half-life t(1/2) = 0.693/k, independent of initial concentration.

How does the half-life of a zero-order reaction depend on initial concentration?

For zero order, t(1/2) = [A0]/(2k), so the half-life is directly proportional to the initial concentration.

State the Arrhenius equation and the meaning of Ea.

k = A.e^(-Ea/RT), where A is the pre-exponential (frequency) factor and Ea is the activation energy, the minimum energy needed for reaction.

How does a catalyst affect a reaction's rate and equilibrium?

A catalyst lowers the activation energy by providing an alternative pathway, speeding up forward and reverse reactions equally; it does not change the equilibrium position or Delta G.

Distinguish physisorption from chemisorption.

Physisorption: weak van der Waals forces, low heat, reversible, decreases with temperature. Chemisorption: chemical bonds, high heat, often irreversible, specific, increases then decreases with temperature.

What is the difference between a lyophilic and a lyophobic colloid?

Lyophilic colloids are solvent-loving, reversible and stable (e.g. starch, gelatin). Lyophobic colloids are solvent-hating, irreversible and need stabilizers (e.g. metal sols).

Define oxidation and reduction in terms of oxidation number.

Oxidation is an increase in oxidation number (loss of electrons); reduction is a decrease in oxidation number (gain of electrons).

What is a disproportionation reaction? Give an example.

A reaction in which the same element is simultaneously oxidized and reduced. Example: 2H2O2 -> 2H2O + O2 (oxygen goes from -1 to -2 and 0).

State the periodic trends in atomic radius across a period and down a group.

Atomic radius decreases across a period (increasing nuclear charge) and increases down a group (additional shells).

Define electronegativity and name the most electronegative element.

Electronegativity is the tendency of an atom to attract a shared pair of electrons in a bond. Fluorine is the most electronegative element.

State Fajans' rules for covalent character in ionic bonds.

Covalent character increases with small cation, large anion, and high charge on the ions (greater polarization).

According to VSEPR theory, what shapes correspond to sp, sp2 and sp3 hybridization?

sp = linear (180), sp2 = trigonal planar (120), sp3 = tetrahedral (109.5 degrees).

Why is the H2 molecule diamagnetic and O2 paramagnetic per molecular orbital theory?

H2 has all electrons paired (bond order 1, diamagnetic). O2 has two unpaired electrons in pi* antibonding orbitals (bond order 2, paramagnetic).

State the diagonal relationship pairs in the periodic table.

Li-Mg, Be-Al, and B-Si show similar properties due to comparable charge/size ratios despite being in different groups and periods.

What is the lanthanide contraction and one of its consequences?

The steady decrease in size of lanthanide ions with increasing atomic number due to poor shielding by 4f electrons; it makes the second and third row transition elements (e.g. Zr/Hf) nearly equal in size.

State Werner's coordination theory terms: primary and secondary valence.

Primary valence = oxidation state (ionizable, satisfied by anions); secondary valence = coordination number (non-ionizable, directional, fixed for a metal).

What are addition and condensation polymers? Give one example of each.

Addition polymers form by repeated addition of monomers with no by-product (e.g. polythene). Condensation polymers form with elimination of small molecules like water (e.g. nylon-6,6).