AKU BScN Admission Test Chemistry Syllabus

State Avogadro's law.

Equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules (V ∝ n at constant T and P).

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 + ...

State Graham's law of diffusion.

The rate of diffusion (or effusion) of a gas is inversely proportional to the square root of its molar mass: rate ∝ 1/√M.

What are the main postulates of the kinetic molecular theory of gases?

Gas molecules are in constant random motion, have negligible volume, exert no intermolecular forces, undergo perfectly elastic collisions, and their average kinetic energy is proportional to absolute temperature.

Why do real gases deviate from ideal behavior, and under what conditions?

Real gases have measurable molecular volume and intermolecular attractions. Deviations are greatest at high pressure and low temperature.

Define evaporation and boiling point.

Evaporation is the escape of liquid molecules from the surface below the boiling point. Boiling point is the temperature at which a liquid's vapor pressure equals the external (atmospheric) pressure.

What is the difference between a crystalline solid and an amorphous solid?

Crystalline solids have a regular, repeating long-range ordered arrangement of particles and sharp melting points; amorphous solids lack long-range order and soften over a range of temperatures (e.g., glass).

Define vapor pressure and state how it relates to boiling point.

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid. A liquid with higher vapor pressure boils at a lower temperature; boiling occurs when vapor pressure equals atmospheric pressure.

What is Avogadro's number and what does it represent?

6.022 × 10²³; the number of particles (atoms, molecules, ions) in one mole of a substance.

How do you calculate the number of moles from mass?

Moles = mass (g) ÷ molar mass (g/mol).

What is the molar volume of an ideal gas at STP?

22.4 litres per mole at standard temperature and pressure (0°C, 1 atm).

How do you calculate the number of particles in a given number of moles?

Number of particles = moles × 6.022 × 10²³ (Avogadro's number).

What is the difference between an empirical formula and a molecular formula?

An empirical formula shows the simplest whole-number ratio of atoms; a molecular formula shows the actual number of each atom in a molecule. Molecular formula = n × empirical formula.

Outline the steps to determine an empirical formula from percentage composition.

1) Assume 100 g so percentages become grams. 2) Divide each element's mass by its atomic mass to get moles. 3) Divide all mole values by the smallest. 4) Convert to whole-number ratios (multiply if needed).

If a compound has empirical formula CH2O and molar mass 180 g/mol, what is its molecular formula?

Empirical mass = 30; n = 180/30 = 6; molecular formula = C6H12O6 (glucose).

What does it mean for a chemical equation to be balanced, and why is it required?

It has equal numbers of each type of atom on both sides, satisfying the law of conservation of mass — matter is neither created nor destroyed in a reaction.

Define limiting reactant and excess reactant.

The limiting reactant is the one completely consumed first and determines the amount of product formed; the excess reactant is left over after the reaction stops.

Define theoretical yield, actual yield, and percentage yield.

Theoretical yield = maximum product predicted by stoichiometry; actual yield = product actually obtained; percentage yield = (actual yield ÷ theoretical yield) × 100.

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

ΔH is the heat content change at constant pressure. Exothermic releases heat (ΔH negative); endothermic absorbs heat (ΔH 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; enthalpy changes of steps can be added to give the overall ΔH.

Write the formula relating heat, mass, specific heat, and temperature change.

q = m × c × ΔT, where q = heat, m = mass, c = specific heat capacity, ΔT = change in temperature.

What factors affect the rate of a chemical reaction?

Concentration (or pressure for gases), temperature, surface area of solids, presence of a catalyst, and the nature of the reactants.

How does a catalyst increase reaction rate?

It provides an alternative reaction pathway with a lower activation energy, without being consumed in the reaction.

Define activation energy.

The minimum amount of energy that reactant molecules must possess for a successful (effective) collision leading to a reaction.

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 (opposes) the change.

Write the equilibrium constant expression (Kc) for: N2 + 3H2 ⇌ 2NH3.

Kc = [NH3]² / ([N2][H2]³).

What does a large value of the equilibrium constant (K) indicate?

That the equilibrium lies to the right, favoring products (the forward reaction predominates).

Write the formula for pH and pOH, and state their relationship at 25°C.

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

Calculate the pH of a 0.001 M HCl solution.

[H+] = 0.001 = 1 × 10⁻³ M, so pH = -log(10⁻³) = 3.

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

Arrhenius: produces H+ in water. Brønsted-Lowry: proton (H+) donor. Lewis: electron-pair acceptor.

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

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

What is salt hydrolysis, and what is the pH of a salt of a strong base and weak acid?

Salt hydrolysis is the reaction of salt ions with water to produce acidic or basic solutions. A salt of a strong base and weak acid (e.g., CH3COONa) gives a basic solution (pH > 7).

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

Oxidation = loss of electrons / increase in oxidation number; Reduction = gain of electrons / decrease in oxidation number (OIL RIG).

In a redox reaction, what are the oxidizing agent and reducing agent?

The oxidizing agent gains electrons (it is itself reduced); the reducing agent loses electrons (it is itself oxidized).

What is the oxidation number of oxygen and hydrogen in most compounds?

Oxygen is usually -2 (except -1 in peroxides, +2 in OF2); hydrogen is usually +1 (except -1 in metal hydrides).

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

A galvanic cell converts chemical energy into electrical energy via a spontaneous reaction; an electrolytic cell uses electrical energy to drive a non-spontaneous reaction.

In a galvanic cell, which electrode is the anode and which is the cathode in terms of charge and reaction?

Anode (negative): oxidation occurs. Cathode (positive): reduction occurs. (In both cell types, oxidation = anode, reduction = cathode.)

Define electrolysis.

The decomposition of an electrolyte (molten or in solution) by passing a direct electric current through it, driving a non-spontaneous redox reaction.

In electrolysis, what happens at the cathode and anode in terms of ion movement?

Cations move to the cathode (negative electrode) and are reduced; anions move to the anode (positive electrode) and are oxidized.

What is a salt bridge and what is its function in a galvanic cell?

A tube containing an inert electrolyte (e.g., KCl) that connects the two half-cells, maintaining electrical neutrality by allowing ion flow and completing the circuit.