IAT Chemistry Syllabus

In Molecular Orbital Theory, how is bond order calculated and what does it indicate?

Bond order = (number of bonding electrons − number of antibonding electrons) / 2. A higher bond order means a stronger, shorter bond; bond order of zero means the molecule does not exist.

Why is O2 paramagnetic according to Molecular Orbital Theory?

In O2, the two highest-energy electrons occupy two degenerate π* (antibonding) orbitals singly with parallel spins, giving two unpaired electrons, which makes O2 paramagnetic.

State Boyle's Law and Charles's Law.

Boyle's Law: at constant temperature, P ∝ 1/V (PV = constant). Charles's Law: at constant pressure, V ∝ T (V/T = constant), with T in kelvin.

Write the ideal gas equation and define each term.

PV = nRT, where P = pressure, V = volume, n = moles, R = universal gas constant (0.0821 L·atm·K⁻¹·mol⁻¹ or 8.314 J·K⁻¹·mol⁻¹), and T = absolute temperature in kelvin.

According to the kinetic theory of gases, how does average kinetic energy relate to temperature?

The average kinetic energy of gas molecules is directly proportional to the absolute temperature: KE_avg = (3/2)kT per molecule. It is independent of the gas's identity.

State the First Law of Thermodynamics and its mathematical form.

Energy can neither be created nor destroyed, only converted. ΔU = q + w, where ΔU = change in internal energy, q = heat added to the system, and w = work done on the system.

Define enthalpy (H) and the enthalpy change at constant pressure.

Enthalpy H = U + PV is the total heat content of a system. At constant pressure, the enthalpy change ΔH equals the heat exchanged (q_p). ΔH < 0 is exothermic; ΔH > 0 is endothermic.

State Hess's Law of constant heat summation.

The total enthalpy change of a reaction is the same whether it occurs in one step or several steps, depending only on the initial and final states (enthalpy is a state function).

Define entropy (S) and state the Second Law of Thermodynamics.

Entropy is a measure of the disorder or randomness of a system. Second Law: the total entropy of the universe always increases for a spontaneous process (ΔS_universe > 0).

What is Gibbs free energy and the criterion for spontaneity?

ΔG = ΔH − TΔS. A process is spontaneous when ΔG < 0, at equilibrium when ΔG = 0, and non-spontaneous when ΔG > 0.

What characterizes a system at dynamic (chemical) equilibrium?

The forward and reverse reaction rates are equal, so the concentrations of reactants and products remain constant over time, though both reactions continue. It is achieved only in a closed system.

State Le Chatelier's principle.

If a system at equilibrium is disturbed by a change in concentration, pressure, or temperature, the equilibrium shifts in the direction that counteracts (partially undoes) the disturbance.

Write the equilibrium constant expression Kc for the reaction aA + bB ⇌ cC + dD.

Kc = ([C]^c [D]^d) / ([A]^a [B]^b), where concentrations are equilibrium molar concentrations. (Pure solids and liquids are excluded.)

What is the ionic product of water (Kw) at 25°C, and how do pH and pOH relate?

Kw = [H+][OH-] = 1.0 x 10^-14 at 25°C. pH = -log[H+], and pH + pOH = 14 at 25°C.

How are acids and bases defined by the Bronsted-Lowry and Lewis concepts?

Bronsted-Lowry: an acid is a proton (H+) donor and a base is a proton acceptor. Lewis: an acid is an electron-pair acceptor and a base is an electron-pair donor.

What is a buffer solution and what does the Henderson-Hasselbalch equation give?

A buffer resists pH change on adding small amounts of acid or base; it contains a weak acid and its conjugate base (or weak base and its salt). pH = pKa + log([salt]/[acid]).

Define oxidation and reduction in terms of electrons and oxidation number.

Oxidation is loss of electrons (increase in oxidation number); reduction is gain of electrons (decrease in oxidation number). They always occur together in a redox reaction (mnemonic: OIL RIG).

What is an oxidizing agent and a reducing agent?

An oxidizing agent accepts electrons (gets reduced) and oxidizes another species. A reducing agent donates electrons (gets oxidized) and reduces another species.

How does a galvanic (voltaic) cell differ from an electrolytic cell?

A galvanic cell converts chemical energy into electrical energy via a spontaneous redox reaction (ΔG < 0). An electrolytic cell uses external electrical energy to drive a non-spontaneous reaction (ΔG > 0).

In a galvanic cell, what reactions occur at the anode and cathode, and what are their signs?

Oxidation occurs at the anode (negative terminal in a galvanic cell); reduction occurs at the cathode (positive terminal). Electrons flow from anode to cathode through the external circuit.

Write the Nernst equation for cell potential at 298 K.

E_cell = E°_cell − (0.0591/n) log Q, where E°_cell is the standard cell potential, n is moles of electrons transferred, and Q is the reaction quotient.

Why is hydrogen placed uniquely in the periodic table, and what are its main allotropic/isotopic forms?

Hydrogen resembles both group 1 (one valence electron, forms H+) and group 17 (one electron short of a noble gas, forms H-), so it has a unique position. Its three isotopes are protium (¹H), deuterium (²H/D), and tritium (³H, radioactive).

What are the three classes of hydrides, with an example of each?

Ionic (saline) hydrides: with s-block metals, e.g. NaH, CaH2. Covalent (molecular) hydrides: with p-block non-metals, e.g. CH4, NH3, H2O. Metallic (interstitial) hydrides: with many d/f-block metals, e.g. TiH2 (often non-stoichiometric).

What general trends characterize the Group 1 alkali metals?

They are soft, low-density, highly reactive metals with one valence electron (ns¹), low ionization energies, forming +1 ions. Reactivity increases down the group; they react vigorously with water to give hydroxides and H2, and impart characteristic flame colors.

How do Group 2 alkaline earth metals compare to Group 1 metals?

Group 2 metals have two valence electrons (ns²), form +2 ions, and are harder, denser, less reactive, with higher melting points and higher ionization energies than the corresponding Group 1 metals. Reactivity increases down the group.

What is the inert pair effect, illustrated in Group 13?

Down Group 13, the ns² electrons become reluctant to participate in bonding, so the lower +1 oxidation state becomes more stable than +3. Thus Tl+ is more stable than Tl³⁺, while boron and aluminium prefer +3.

Why does carbon (Group 14) show catenation and what is the trend down the group?

Carbon forms strong, stable C–C bonds allowing extensive catenation (long chains/rings). Catenation tendency decreases down the group (C > Si > Ge > Sn > Pb) as bond strength decreases, and metallic character increases (C non-metal to Pb metal).

How are organic compounds broadly classified by structure?

Into acyclic (open-chain/aliphatic) compounds and cyclic compounds. Cyclic divides into homocyclic (carbocyclic: alicyclic and aromatic) and heterocyclic. Aromatic compounds contain benzene-type rings; aliphatic do not.

State the basic IUPAC nomenclature rules for naming a simple organic compound.

Identify the longest continuous carbon chain (parent/root), number it to give substituents/functional groups the lowest locants, name substituents as prefixes (alphabetical), and indicate the principal functional group with a suffix. Format: locant-prefix + root + suffix.

Distinguish structural isomerism from stereoisomerism.

Structural (constitutional) isomers differ in the connectivity of atoms (e.g. chain, position, functional group, metamerism). Stereoisomers have the same connectivity but differ in spatial arrangement (geometrical cis-trans and optical isomers).

What is the general formula and key reaction type of alkanes?

Alkanes have the general formula CnH2n+2; they are saturated hydrocarbons with only single bonds. They are relatively unreactive and undergo substitution reactions (e.g. free-radical halogenation) and combustion.

What is the general formula of alkenes and their characteristic reaction, including Markovnikov's rule?

Alkenes: CnH2n, containing a C=C double bond; they undergo electrophilic addition reactions. Markovnikov's rule: in addition of HX to an unsymmetrical alkene, H adds to the carbon already having more hydrogens (the X goes to the more substituted carbon).

What is the general formula of alkynes and how does the acidity of terminal alkynes arise?

Alkynes: CnH2n-2, containing a C≡C triple bond. Terminal alkynes (≡C–H) are weakly acidic because the sp-hybridized carbon holds the C–H electrons more tightly, so the H can be replaced by metals to form acetylides.

What is Huckel's rule for aromaticity?

A planar, cyclic, fully conjugated ring is aromatic if it contains (4n + 2) delocalized π electrons (where n = 0, 1, 2, ...). For example, benzene has 6 π electrons (n = 1).

What is the characteristic reaction of aromatic hydrocarbons like benzene, and name examples?

They undergo electrophilic aromatic substitution (preserving the aromatic ring) rather than addition. Examples: nitration, halogenation, sulphonation, and Friedel-Crafts alkylation/acylation.

What are the major types of environmental pollution and key pollutants?

Air pollution (CO, SO2, NO_x, particulates, CFCs), water pollution (sewage, heavy metals, fertilizers causing eutrophication), and soil pollution (pesticides, industrial waste). Major effects include acid rain (SO2, NO_x), ozone depletion (CFCs), and global warming (CO2, CH4).

What causes acid rain and what are its main chemical components?

Acid rain is caused by oxides of sulphur and nitrogen (SO2, NO_x) released from burning fossil fuels, which react with atmospheric water to form sulphuric acid (H2SO4) and nitric acid (HNO3), lowering rain pH below 5.6.

What is the greenhouse effect and which gases are mainly responsible?

The greenhouse effect is the trapping of infrared (heat) radiation by atmospheric gases, warming the Earth. Main greenhouse gases: carbon dioxide (CO2), methane (CH4), water vapor, nitrous oxide (N2O), and CFCs; their buildup causes global warming.

What is molarity and how does it differ from molality?

Molarity (M) = moles of solute per litre of solution (depends on temperature). Molality (m) = moles of solute per kilogram of solvent (independent of temperature).

How does hybridization (sp, sp2, sp3) relate to molecular geometry and bond angle?

sp hybridization gives linear geometry (180°), sp2 gives trigonal planar (120°), and sp3 gives tetrahedral (109.5°). The number of hybrid orbitals equals the number of sigma bonds plus lone pairs on the central atom.

State Dalton's Law of Partial Pressures.

The total pressure of a mixture of non-reacting gases equals the sum of the partial pressures of the individual gases: P_total = P1 + P2 + P3 + ... Each partial pressure is the pressure that gas would exert alone in the same volume.