Q. In which of the following molecules does the molecular orbital theory predict a triple bond?
A.N2
B.O2
C.C2
D.H2
Solution
N2 has a triple bond, with a bond order of 3 according to molecular orbital theory.
Correct Answer: A — N2
Q. In which of the following molecules does the molecular orbital theory predict a paramagnetic behavior?
A.N2
B.O2
C.C2
D.Ne2
Solution
O2 is paramagnetic due to the presence of two unpaired electrons in its molecular orbitals.
Correct Answer: B — O2
Q. In which of the following reactions is the enthalpy change likely to be the largest?
A.Dissolving salt in water
B.Combustion of gasoline
C.Melting of ice
D.Sublimation of dry ice
Solution
The combustion of gasoline releases a large amount of energy, resulting in a large enthalpy change.
Correct Answer: B — Combustion of gasoline
Q. In which of the following reactions is the entropy change expected to be negative?
A.N2(g) + 3H2(g) → 2NH3(g)
B.C(s) + O2(g) → CO2(g)
C.2H2(g) + O2(g) → 2H2O(g)
D.CaCO3(s) → CaO(s) + CO2(g)
Solution
The reaction N2(g) + 3H2(g) → 2NH3(g) results in a decrease in the number of gas molecules, leading to a negative change in entropy.
Correct Answer: A — N2(g) + 3H2(g) → 2NH3(g)
Q. In which of the following scenarios would the entropy of the system decrease?
A.Ice melting
B.Water evaporating
C.Gas compressing
D.Sugar dissolving in water
Solution
When a gas is compressed, the number of microstates decreases, leading to a decrease in entropy.
Correct Answer: C — Gas compressing
Q. In which of the following species does the molecular orbital configuration show a paramagnetic behavior?
A.N2
B.O2
C.F2
D.Ne2
Solution
O2 has unpaired electrons in its molecular orbital configuration, making it paramagnetic.
Correct Answer: B — O2
Q. In which of the following states does a liquid exhibit the highest density?
A.At low temperatures
B.At high temperatures
C.At critical temperature
D.At boiling point
Solution
Liquids generally exhibit the highest density at low temperatures.
Correct Answer: A — At low temperatures
Q. In which of the following states of matter do particles have the least freedom of movement?
A.Solid
B.Liquid
C.Gas
D.Plasma
Solution
In solids, particles are closely packed and have limited movement.
Correct Answer: A — Solid
Q. In which process does the entropy of the system decrease?
A.Freezing of water
B.Evaporation of water
C.Sublimation of dry ice
D.Dissolving salt in water
Solution
The freezing of water results in a decrease in the entropy of the system as it transitions from liquid to solid.
Correct Answer: A — Freezing of water
Q. In which scenario would the Gibbs Free Energy of a system be at its minimum?
A.At equilibrium
B.At the start of a reaction
C.At maximum temperature
D.At maximum pressure
Solution
The Gibbs Free Energy of a system is at its minimum at equilibrium, indicating stability.
Correct Answer: A — At equilibrium
Q. In which scenario would ΔG be equal to ΔH?
A.At absolute zero.
B.When ΔS = 0.
C.For a spontaneous reaction.
D.For an endothermic reaction.
Solution
ΔG equals ΔH when the entropy change (ΔS) is zero, indicating no change in disorder.
Correct Answer: B — When ΔS = 0.
Q. In which scenario would ΔG be zero?
A.At standard conditions
B.At equilibrium
C.In a spontaneous reaction
D.In a non-spontaneous reaction
Solution
ΔG is zero at equilibrium, indicating no net change in the concentrations of reactants and products.
Correct Answer: B — At equilibrium
Q. In which state of matter do particles have the highest kinetic energy?
A.Solid
B.Liquid
C.Gas
D.Plasma
Solution
Plasma has the highest kinetic energy as the particles are highly energized and ionized.
Correct Answer: D — Plasma
Q. In which type of reaction is the change in enthalpy equal to the heat absorbed or released at constant pressure?
A.Endothermic reaction
B.Exothermic reaction
C.Isothermal reaction
D.Adiabatic reaction
Solution
In an endothermic reaction, the change in enthalpy is equal to the heat absorbed at constant pressure.
Correct Answer: A — Endothermic reaction
Q. The Arrhenius equation relates the rate constant to which of the following?
A.Temperature and concentration
B.Temperature and activation energy
C.Concentration and pressure
D.Temperature and volume
Solution
The Arrhenius equation relates the rate constant to temperature and activation energy.
Correct Answer: B — Temperature and activation energy
Q. The enthalpy change for a reaction can be calculated using which of the following?
A.Bond energies
B.Standard enthalpies of formation
C.Calorimetry
D.All of the above
Solution
The enthalpy change for a reaction can be calculated using bond energies, standard enthalpies of formation, and calorimetry.
Correct Answer: D — All of the above
Q. The enthalpy of vaporization of a substance is defined as:
A.The heat required to melt the substance
B.The heat required to convert a liquid into a gas
C.The heat released during condensation
D.The heat required to raise the temperature of a substance
Solution
The enthalpy of vaporization is the heat required to convert a liquid into a gas at constant temperature and pressure.
Correct Answer: B — The heat required to convert a liquid into a gas
Q. The enthalpy of vaporization of water is approximately:
A.40.79 kJ/mol
B.2260 kJ/mol
C.100 kJ/mol
D.60 kJ/mol
Solution
The enthalpy of vaporization of water is approximately 2260 kJ/mol.
Correct Answer: B — 2260 kJ/mol
Q. The entropy change for a reaction can be calculated using which of the following?
A.ΔS = ΣS(products) - ΣS(reactants)
B.ΔS = ΣS(reactants) - ΣS(products)
C.ΔS = Q/T
D.ΔS = W/T
Solution
The change in entropy for a reaction is calculated using the formula ΔS = ΣS(products) - ΣS(reactants).
Correct Answer: A — ΔS = ΣS(products) - ΣS(reactants)
Q. The entropy of a perfect crystal at absolute zero is given by:
A.R
B.0
C.∞
D.1
Solution
According to the third law of thermodynamics, the entropy of a perfect crystal at absolute zero is zero.
Correct Answer: B — 0
Q. The entropy of a perfect crystal at absolute zero is:
A.Maximum
B.Minimum
C.Undefined
D.Infinite
Solution
According to the third law of thermodynamics, the entropy of a perfect crystal at absolute zero is zero, which is the minimum value.
Correct Answer: B — Minimum
Q. The entropy of a perfect crystalline substance at absolute zero is given by which law?
A.Third law of thermodynamics
B.First law of thermodynamics
C.Second law of thermodynamics
D.Zeroth law of thermodynamics
Solution
The third law of thermodynamics states that the entropy of a perfect crystalline substance approaches zero as the temperature approaches absolute zero.
Correct Answer: A — Third law of thermodynamics
Q. The entropy of a perfect crystalline substance at absolute zero is:
A.Zero
B.Maximum
C.Undefined
D.Infinite
Solution
According to the third law of thermodynamics, the entropy of a perfect crystalline substance at absolute zero is zero.
Correct Answer: A — Zero
Q. The Freundlich adsorption isotherm is applicable to which type of adsorption?
A.Physisorption only
B.Chemisorption only
C.Both physisorption and chemisorption
D.None of the above
Solution
The Freundlich isotherm can describe both physisorption and chemisorption processes.
Correct Answer: C — Both physisorption and chemisorption
Q. The half-life of a first-order reaction is dependent on which of the following?
A.Initial concentration
B.Rate constant
C.Temperature
D.All of the above
Solution
The half-life of a first-order reaction is given by t1/2 = 0.693/k, which depends only on the rate constant.
Correct Answer: B — Rate constant
Q. The Langmuir adsorption isotherm assumes that:
A.Adsorption occurs on a surface with infinite sites
B.Adsorption sites are equivalent
C.Adsorption is a multilayer process
D.Adsorption is independent of pressure
Solution
The Langmuir isotherm assumes that adsorption sites are equivalent and that the process is monolayer.
Correct Answer: B — Adsorption sites are equivalent
Q. The phenomenon of surface tension is primarily due to which type of forces?
A.Cohesive forces
B.Adhesive forces
C.Gravitational forces
D.Electrostatic forces
Solution
Surface tension arises from cohesive forces between liquid molecules.
Correct Answer: A — Cohesive forces
Q. The rate law for a reaction is determined experimentally and is dependent on which of the following?
A.Stoichiometry of the reaction
B.Mechanism of the reaction
C.Equilibrium constant
D.Temperature only
Solution
The rate law for a reaction is determined experimentally and is dependent on the mechanism of the reaction.
Correct Answer: B — Mechanism of the reaction
Q. The rate law for a reaction is determined experimentally. Which of the following is true?
A.It can be derived from stoichiometry
B.It is always first-order
C.It depends on the mechanism
D.It is independent of temperature
Solution
The rate law for a reaction depends on the mechanism of the reaction.
Correct Answer: C — It depends on the mechanism
Q. The rate law for a reaction is given as rate = k[A][B]². What is the overall order of the reaction?
A.1
B.2
C.3
D.4
Solution
The overall order of the reaction is the sum of the powers of the concentration terms, which is 1 + 2 = 3.
