University Chemistry Review: Scientific Skills, Matter, and Material Applications, and Formulas

SCIENTIFIC SKILLS AND GREEN CHEMISTRY

• Data Representation: Line graphs are standard for continuous data. Independent variables (manipulated) are plotted on the x-axis, and dependent variables (results) on the y-axis.

• Data Estimation:

  • Interpolation: Estimating points within the range of plotted data.

  • Extrapolation: Predicting points beyond the known data by extending the line of best fit (drawn as dotted/dashed lines).

• Safety Equipment: Eyewash fountains (flush eyes/face for at least 15 minutes) and safety showers (flush body for at least 15 minutes and remove contaminated clothing).

• Laboratory Techniques:

  • Reflux: Boiling solvent with a condenser to return vapor to the flask, allowing long-term heating without losing volatile reactants/products.

  • Distillation: Separates components based on different boiling points.

  • Melting Point: Pure substances have sharp melting points (range of $0.5-1.0\,^℃$). Impurities decrease the melting point and broaden the range.

• Green Chemistry: Redesigning processes to minimize hazardous waste, use renewable materials, and increase efficiency.

• Atom Economy Formula:     $\text{Atom economy} = \frac{\text{Molecular weight of the desired product}}{\text{Sum of the molecular weight of all substances produced}} \times 100$

ATOMIC STRUCTURE AND BONDING

• Relative Atomic Mass (RAM): The mass of an atom compared to Carbon-12.     $\text{RAM} = \frac{\sum (\text{Percentage Abundance} \times \text{atomic mass})}{100}$

• Quantum Numbers:

  • Principal ($n$): Shell/energy level ($1, 2, 3...$).

  • Secondary ($l$): Orbital shape/subshell (s=0, p=1, d=2).

  • Magnetic ($m_l$): Orientation in space ($-l$ to $+l$).

  • Spin ($ms$): Direction of spin ($+\frac{1}{2}$ or $-\frac{1}{2}$).

• Electron Filling Rules:

  • Aufbau Principle: Fill lowest energy orbitals first ($1s, 2s, 2p, 3s, 3p, 4s, 3d...$).

  • Hund’s Rule: Fill orbitals of equal energy singularly before pairing.

  • Pauli Exclusion Principle: No two electrons can have the same four quantum numbers.

• Periodic Trends:

  • Atomic Radius: Decreases across a period (increased effective nuclear charge); increases down a group (added shells/shielding).

  • Ionisation Energy: Energy to remove a gaseous electron. Increases across a period; decreases down a group.

  • Electronegativity: Attraction for shared electrons. Increases across a period; decreases down a group.

• Molecular Geometry (VSEPR): Shape is determined by minimizing electron pair repulsion: \text{Lone Pair:Lone Pair} > \text{Lone Pair:Bond Pair} > \text{Bond Pair:Bond Pair}.

• Intermolecular Forces: Hydrogen bonding ($H$ bonded to $F$, $O$, or $N$) is the strongest, followed by permanent dipole-dipole, then induced dipole (London dispersion) forces.

STATES OF MATTER AND SOLUTIONS

• Ideal Gas Postulates: Particles are in constant random motion, have negligible volume, and collisions are perfectly elastic.

• Gas Laws:

  • Boyle’s: $P_1V_1 = P_2V_2$

  • Charles’s: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$

  • Dalton’s Law of Partial Pressure: $P_{\text{total}} = P_a + P_b + P_c...$

  • Ideal Gas Law: $PV = nRT$ (where $R = 8.314\,JK^{-1}mol^{-1}$).

• Solution Concentration:

  • Molarity ($M$): $\frac{\text{moles of solute}}{\text{Volume of solution in } dm^3}$

  • Molality ($m$): $\frac{\text{moles of solute}}{\text{kilogram of solvent}}$

  • Mole Fraction ($Xa$): $\frac{n_a}{n_{\text{total}}}$

PHYSICAL CHEMISTRY

• Electrochemistry:

  • Oxidation: Increase in oxidation number; loss of electrons.

  • Reduction: Decrease in oxidation number; gain of electrons.

  • Galvanic Cell: Spontaneous reaction generates electricity. Anode is negative; Cathode is positive.

  • Electrolytic Cell: External electricity drives a non-spontaneous reaction. Anode is positive; Cathode is negative.

  • Cell Potential: $E^{\circ}_{\text{cell}} = E^{\circ}_{\text{reduced(cathode)}} - E^{\circ}_{\text{reduced(anode)}}$. Spontaneous if $E^{\circ}_{\text{cell}}$ is positive.

• Thermochemistry:

  • Exothermic: \Delta H < 0 (heat released).

  • Endothermic: \Delta H > 0 (heat absorbed).

  • Specific Heat Capacity ($c$): Heat to raise $1\,g$ of substance by $1\,^℃$. Formula: $H = m \times c \times \Delta T$.

  • Hess’s Law: Total enthalpy change is independent of the pathway taken.

• Aqueous Equilibrium:

  • Equilibrium Constant ($K_c$): $\frac{[\text{Products}]}{[\text{Reactants}]}$. Solids and pure liquids are excluded.

  • Acids and Bases: Bronsted-Lowry (proton donor/acceptor) and Lewis (electron pair acceptor/donor).

  • pH Calculations: $pH = -\log[H_3O^+]$; $pKa = -\log Ka$. High $Ka$/low $pKa$ indicates a strong acid.

  • Buffer Solutions: Resist pH changes when small amounts of acid or base are added.

  • Solubility Product ($K_{sp}$): If Ionic Product ($IP$) > K_{sp}, a precipitate forms.

INORGANIC AND ORGANIC CHEMISTRY

• Inorganic Trends:

  • Hydrides: Period 2 and 3 hydrides shift from basic/ionic ($NaH$) to acidic/covalent ($HCl$) across the period.

  • Transition Metals: Located in the d-block. Characteristics include variable oxidation states, catalytic activity, and colored compounds (due to d-orbital splitting).

  • Complex Ions: Central metal ion bonded to ligands (anions or neutral molecules) via dative covalent bonds.

• Organic Isomerism:

  • Structural: Chain, Position, and Functional Group.

  • Stereoisomerism: Geometrical (cis/trans around double bonds) and Optical (mirror images/enantiomers from chiral carbons).

• Organic Reactions:

  • Markovnikov’s Rule: In addition to unsymmetrical alkenes, $H$ attaches to the carbon with more existing hydrogen atoms.

  • Benzene: Undergoes substitution (not addition) to maintain resonance stability.

• Priority of Functional Groups: Carboxylic acids > Esters > Acyl chlorides > Amides > Aldehydes > Ketones > Alcohols > Amines > Alkenes/Alkynes > Alkanes.

CONSUMER CHEMISTRY (POLYMERS)

• Definitions: Polymers are giant molecules made of repeating monomer units.

• Natural Polymers: Silk, wool, cellulose, starch, proteins.

• Synthetic Polymers: Nylon, polythene, PVC, Teflon, polyester.

• Polymerization Types:

  • Addition: Monomers join without losing atoms (e.g., Ethene $\rightarrow$ Polythene).

  • Condensation: Monomers join while losing a small molecule, usually water (e.g., Polyamides, Polyesters).

• Environmental Impact: Non-biodegradable polymers cause pollution and release toxins if incinerated poorly; biodegradation requires microbial/enzymatic action.