UVAS DVM Admission Test Chemistry Syllabus

State Hund's rule of maximum multiplicity.

Electrons occupy degenerate (equal-energy) orbitals singly with parallel spins before any orbital is doubly occupied.

State the Aufbau principle.

Electrons fill orbitals starting from the lowest available energy level before filling higher ones (e.g., 1s before 2s, 2s before 2p).

Write the ground-state electronic configuration of an atom with 17 electrons (chlorine).

1s2 2s2 2p6 3s2 3p5.

State the postulates of the kinetic molecular theory of gases.

Gas particles are tiny, in constant random motion, have negligible volume, exert no intermolecular forces, undergo elastic collisions, and average KE is proportional to absolute temperature.

State Boyle's law and its equation.

At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure: PV = constant, or P1V1 = P2V2.

State Charles's law and its equation.

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

State Avogadro's law.

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

Write the ideal gas equation and define each term.

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

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 + ...

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

London dispersion forces < dipole-dipole forces < hydrogen bonding (all weaker than ionic/covalent bonds).

What is hydrogen bonding and between which atoms does it occur?

A strong dipole-dipole attraction between H bonded to a highly electronegative atom (F, O, or N) and a lone pair on F, O, or N of a neighboring molecule.

Why does water have an unusually high boiling point?

Because of extensive hydrogen bonding between water molecules, which requires extra energy to break.

What is the relationship between intermolecular forces and a liquid's vapor pressure and boiling point?

Stronger intermolecular forces give lower vapor pressure and higher boiling point; weaker forces give higher vapor pressure and lower boiling point.

Name the four main types of crystalline solids.

Ionic, covalent (network/giant), metallic, and molecular crystals.

Compare ionic and molecular crystals in terms of melting point and hardness.

Ionic crystals have high melting points and are hard but brittle; molecular crystals have low melting points and are soft due to weak intermolecular forces.

Give an example of a covalent network solid and a property it has.

Diamond (or SiO2/quartz); it is very hard with a very high melting point due to a continuous network of strong covalent bonds.

What is a reversible reaction?

A reaction in which products can react to re-form the reactants; it can proceed in both forward and backward directions, shown with a double arrow.

Define chemical equilibrium.

The state of a reversible reaction where the rates of the forward and reverse reactions are equal, so the concentrations of reactants and products remain constant.

For the reaction aA + bB <=> cC + dD, write the equilibrium constant expression Kc.

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

What does a large Kc value (Kc >> 1) indicate about a reaction at equilibrium?

That products are favored; at equilibrium the mixture contains mostly products.

State Le Chatelier's principle.

If a system at equilibrium is disturbed by a change in concentration, temperature, or pressure, the equilibrium shifts to counteract (oppose) that change.

According to Le Chatelier's principle, how does increasing pressure affect a gaseous equilibrium?

The equilibrium shifts toward the side with fewer moles of gas to reduce the pressure.

How does increasing temperature affect an exothermic equilibrium reaction?

It shifts the equilibrium in the reverse (endothermic) direction, decreasing the yield of products and decreasing Kc.

What is Kp, and how is it related to Kc?

Kp is the equilibrium constant in terms of partial pressures of gases. Kp = Kc(RT)^(delta n), where delta n = (moles of gaseous products) - (moles of gaseous reactants).

Define the rate of a chemical reaction.

The change in concentration of a reactant or product per unit time (e.g., mol dm^-3 s^-1).

For the rate law Rate = k[A]^m[B]^n, what do m and n represent?

m and n are the orders of reaction with respect to A and B; the overall order is m + n. They are determined experimentally.

How is the order of a reaction defined?

The order is the sum of the powers to which the concentration terms are raised in the experimentally determined rate law.

List the main factors that affect the rate of a reaction.

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

How does a catalyst increase the rate of a reaction?

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

State the first law of thermodynamics and the equation relating internal energy, heat, and work.

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

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 (because enthalpy is a state function).