COMSATS NTS-based Test Chemistry (NAT-IE / NAT-IM) Syllabus

State Charles's law and its mathematical form.

At constant pressure, the volume of a fixed gas mass is directly proportional to its absolute temperature: V/T = constant, or V1/T1 = V2/T2.

Write the ideal gas equation and define each term.

PV = nRT, where P = pressure, V = volume, n = moles, R = gas constant (8.314 J/mol/K), T = absolute temperature in kelvin.

State Avogadro's law.

Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules; volume is directly proportional to number of moles (V proportional to n).

Define the dynamic equilibrium of a reversible reaction.

A state where the forward and reverse reaction rates are equal, so the concentrations of reactants and products remain constant over time (though both reactions continue).

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 the change.

Write the equilibrium constant expression Kc for the reaction aA + bB <=> cC + dD.

Kc = [C]^c [D]^d / ([A]^a [B]^b), using equilibrium molar concentrations.

How does increasing pressure affect the position of a gaseous equilibrium?

It shifts the equilibrium toward the side with fewer moles of gas (smaller volume), to reduce the pressure.

In an exothermic reaction at equilibrium, what is the effect of increasing temperature on Kc and on yield?

It shifts equilibrium toward reactants (backward), decreasing the yield of products and decreasing Kc.

Does a catalyst change the position of equilibrium or the value of Kc?

No. A catalyst speeds up forward and reverse reactions equally, reaching equilibrium faster without changing its position or Kc.

Define enthalpy change (delta H) and distinguish exothermic from endothermic reactions.

delta H is the heat change at constant pressure. Exothermic: heat released, delta H is negative. Endothermic: heat absorbed, delta H is positive.

State Hess's law.

The total enthalpy change of a reaction is independent of the route taken, depending only on the initial and final states (since enthalpy is a state function).

Define standard enthalpy of formation (delta Hf).

The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions (298 K, 1 atm). For elements it is zero.

Define enthalpy of combustion.

The enthalpy change when one mole of a substance is completely burned in excess oxygen under standard conditions; always exothermic (negative).

Write the calorimetry equation used to calculate heat absorbed or released.

q = m c delta T, where m = mass, c = specific heat capacity, delta T = temperature change.

What are the periods and groups in the periodic table, and what does each correspond to?

Periods are horizontal rows (same number of electron shells); groups are vertical columns (same number of valence electrons / similar chemical properties).

Describe the trend in atomic radius across a period and down a group, with reasons.

Across a period it decreases (increasing nuclear charge pulls electrons closer); down a group it increases (more shells added).

Describe the trend in ionization energy across a period and down a group.

Ionization energy increases across a period (greater nuclear charge, smaller size) and decreases down a group (electrons farther from nucleus, more shielding).

How does metallic vs non-metallic character vary across a period and down a group?

Metallic character decreases across a period and increases down a group; non-metallic character does the opposite.

What is the general trend in electron affinity across a period?

Electron affinity generally becomes more negative (more energy released) across a period as atoms more readily gain electrons, with halogens having the highest values.

Name the s-block, p-block, d-block, and f-block in terms of the subshell being filled.

s-block = outermost s subshell filling (Groups 1-2); p-block = p subshell (Groups 13-18); d-block = d subshell (transition metals); f-block = f subshell (lanthanides/actinides).

Why are Group 1 elements called alkali metals and how does their reactivity change down the group?

They react with water to form alkaline (basic) hydroxides. Reactivity increases down the group as ionization energy decreases and the outer electron is more easily lost.

What is the general trend in reactivity of Group 17 (halogens) down the group, and why?

Reactivity decreases down the group because atomic size increases and the ability to attract/gain an electron (electronegativity) decreases.

List three characteristic properties of transition elements.

They form colored ions/compounds, show variable oxidation states, act as catalysts, and form complex ions (paramagnetic due to unpaired d electrons).

Why do transition metals exhibit variable oxidation states?

Because the energies of the 3d and 4s electrons are very close, allowing a variable number of electrons from both to participate in bonding.

Why are transition metal complexes often colored?

d-orbitals split into different energy levels in a ligand field; electrons absorb specific wavelengths of visible light during d-d transitions, and the complementary color is seen.

Define a homologous series and give its key features.

A family of organic compounds with the same general formula, similar chemical properties, and a gradation in physical properties, with each member differing from the next by a CH2 unit.

Compare the general reactivity of alkanes, alkenes, and alkynes.

Alkanes are saturated and relatively unreactive (undergo substitution); alkenes and alkynes are unsaturated and more reactive, undergoing addition reactions at their double/triple bonds.

What is the difference between substitution and addition reactions?

In substitution, an atom or group replaces another in a (usually saturated) molecule; in addition, atoms add across a double or triple bond, converting unsaturated to saturated.

Identify the functional group and a characteristic suffix for alcohols, aldehydes, ketones, and carboxylic acids.

Alcohol = -OH (-ol); aldehyde = -CHO (-al); ketone = C=O between carbons (-one); carboxylic acid = -COOH (-oic acid).

Distinguish electrophiles from nucleophiles.

Electrophiles are electron-pair acceptors (electron-deficient, e.g. H+, NO2+); nucleophiles are electron-pair donors (electron-rich, e.g. OH-, NH3, CN-).

Define the mole and Avogadro's number.

A mole is the amount of substance containing as many particles as there are atoms in 12 g of carbon-12; Avogadro's number = 6.022 x 10^23 particles per mole.

Write the formulas relating moles to mass, to number of particles, and to gas volume at STP.

moles = mass / molar mass; moles = number of particles / 6.022 x 10^23; moles of gas at STP = volume / 22.4 L.