OAT (Optometry Admission Test) General Chemistry Syllabus

What are the products of complete combustion of a hydrocarbon?

Carbon dioxide (CO₂) and water (H₂O).

What does it mean to balance a chemical equation, and what principle requires it?

Equal numbers of each type of atom must appear on both sides; required by the law of conservation of mass. Only coefficients (not subscripts) may be changed.

What is a limiting reagent?

The reactant that is completely consumed first, thereby limiting the amount of product that can be formed.

How do you calculate percent yield?

Percent yield = (actual yield / theoretical yield) × 100%.

Define oxidation and reduction in terms of electrons.

Oxidation is the loss of electrons (increase in oxidation state); reduction is the gain of electrons (decrease in oxidation state). 'OIL RIG'.

What is the oxidizing agent versus the reducing agent in a redox reaction?

The oxidizing agent is reduced (gains electrons, causes oxidation of another); the reducing agent is oxidized (loses electrons, causes reduction of another).

What are the common oxidation number rules for free elements, monatomic ions, oxygen, and hydrogen?

Free element = 0; monatomic ion = its charge; oxygen usually = -2 (-1 in peroxides); hydrogen usually = +1 (-1 with metals).

State the ideal gas law and define each variable.

PV = nRT, where P = pressure, V = volume, n = moles, R = gas constant (0.0821 L·atm/mol·K), T = temperature in Kelvin.

State Boyle's law and Charles's law.

Boyle's: at constant T, P and V are inversely proportional (P₁V₁ = P₂V₂). Charles's: at constant P, V and T are directly proportional (V₁/T₁ = V₂/T₂).

State Dalton's law of partial pressures.

The total pressure of a gas mixture equals the sum of the partial pressures of each component gas: P_total = P₁ + P₂ + P₃ + ...

What does Graham's law of effusion state about gas rates and molar mass?

The rate of effusion is inversely proportional to the square root of molar mass: rate₁/rate₂ = √(M₂/M₁). Lighter gases effuse faster.

Name the six phase transitions between solid, liquid, and gas.

Melting (s→l), freezing (l→s), vaporization (l→g), condensation (g→l), sublimation (s→g), and deposition (g→s).

List the major types of intermolecular forces from weakest to strongest.

London dispersion forces < dipole-dipole forces < hydrogen bonding (and ion-dipole as the strongest of the noncovalent attractions).

What is the difference between a solute, solvent, and solution?

Solute = substance being dissolved (lesser amount); solvent = the dissolving medium (greater amount); solution = the resulting homogeneous mixture.

How is molarity defined and calculated?

Molarity (M) = moles of solute / liters of solution.

What is the dilution equation?

M₁V₁ = M₂V₂ (moles of solute remain constant during dilution).

What are the four colligative properties of solutions?

Vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure. They depend on the number of solute particles, not their identity.

What is the formula for freezing point depression and boiling point elevation?

ΔT_f = i·K_f·m and ΔT_b = i·K_b·m, where i = van't Hoff factor, K = molal constant, and m = molality.

What is the van't Hoff factor (i)?

The number of dissolved particles produced per formula unit of solute (e.g., NaCl → i ≈ 2, glucose → i = 1).

What is the difference between an exothermic and an endothermic process in terms of ΔH?

Exothermic releases heat (ΔH < 0, negative); endothermic absorbs heat (ΔH > 0, positive).

State Hess's law.

The total enthalpy change of a reaction is the same regardless of the pathway; enthalpies of individual steps can be summed to give the overall ΔH.

What is the equation relating heat, mass, specific heat, and temperature change?

q = mcΔT, where q = heat, m = mass, c = specific heat, and ΔT = temperature change.

State the first and second laws of thermodynamics.

First law: energy is conserved (ΔU = q + w; energy cannot be created or destroyed). Second law: the total entropy of an isolated system always increases for a spontaneous process.

What is the Gibbs free energy equation, and what does the sign of ΔG indicate?

ΔG = ΔH - TΔS. ΔG < 0 = spontaneous, ΔG > 0 = nonspontaneous, ΔG = 0 = at equilibrium.

Under what combinations of ΔH and ΔS is a reaction always spontaneous or never spontaneous?

Always spontaneous when ΔH < 0 and ΔS > 0; never spontaneous when ΔH > 0 and ΔS < 0 (other combinations are temperature-dependent).

What factors increase the rate of a chemical reaction?

Higher concentration, higher temperature, increased surface area, and presence of a catalyst.

How does a catalyst increase reaction rate?

It provides an alternative reaction pathway with a lower activation energy, without being consumed and without changing ΔG or the equilibrium position.

What is the rate law and the order of a reaction?

Rate = k[A]^m[B]^n; the reaction order is the sum of exponents (m + n), determined experimentally, indicating how concentration affects rate.

State Le Chatelier's principle.

When a system at equilibrium is disturbed by a change in concentration, pressure, volume, or temperature, the equilibrium shifts to counteract the change and restore equilibrium.

What is the equilibrium constant expression Keq for aA + bB ⇌ cC + dD?

Keq = [C]^c[D]^d / [A]^a[B]^b (pure solids and liquids are excluded).

Compare the Arrhenius, Brønsted-Lowry, and Lewis definitions of acids.

Arrhenius acid produces H⁺ in water; Brønsted-Lowry acid is a proton (H⁺) donor; Lewis acid is an electron-pair acceptor.

What are the formulas for pH and pOH, and what is their relationship at 25°C?

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

What is a buffer solution and what is it made of?

A solution that resists changes in pH; made of a weak acid and its conjugate base (or a weak base and its conjugate acid).

What is the Henderson-Hasselbalch equation?

pH = pKa + log([A⁻]/[HA]), relating pH to the pKa and the ratio of conjugate base to weak acid.

What is the equivalence point in a titration?

The point at which moles of added titrant exactly equal the moles of analyte (stoichiometrically equivalent), determined using moles acid = moles base for a monoprotic neutralization.

What is Ksp and what does a larger Ksp indicate?

Ksp is the solubility product constant for a slightly soluble ionic compound; a larger Ksp indicates greater solubility.

What is the common-ion effect on solubility?

The solubility of an ionic compound decreases when a soluble salt sharing a common ion is added (equilibrium shifts toward the solid per Le Chatelier's principle).

What is the difference between a galvanic (voltaic) cell and an electrolytic cell?

A galvanic cell uses a spontaneous redox reaction to generate electricity (ΔG < 0, E°cell > 0); an electrolytic cell uses electrical energy to drive a nonspontaneous reaction (ΔG > 0).

In any electrochemical cell, at which electrode do oxidation and reduction occur?

Oxidation always occurs at the anode; reduction always occurs at the cathode ('An Ox, Red Cat').

What is the relationship between standard cell potential and Gibbs free energy?

ΔG° = -nFE°cell, where n = moles of electrons and F = Faraday's constant. A positive E°cell gives negative ΔG° (spontaneous).

What are alpha, beta, and gamma radiation?

Alpha = helium nucleus (²₄He, +2 charge); beta = high-energy electron (⁰₋₁e); gamma = high-energy electromagnetic photon (no mass or charge).

What is the definition of radioactive half-life?

The time required for half of a given quantity of a radioactive isotope to decay.

What is the difference between nuclear fission and nuclear fusion?

Fission splits a heavy nucleus into lighter nuclei (releasing energy); fusion combines light nuclei into a heavier one (releasing even more energy, as in stars).

What is the difference between accuracy and precision?

Accuracy is closeness of a measurement to the true value; precision is the reproducibility/closeness of repeated measurements to one another.

What does the Beer-Lambert law state in spectrophotometry?

Absorbance is directly proportional to concentration and path length: A = εbc, where ε = molar absorptivity, b = path length, c = concentration.