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
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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
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Q. The enthalpy change for the reaction A + B → C is +50 kJ/mol. What can be said about the reaction?
A.
It is exothermic
B.
It is endothermic
C.
It is spontaneous
D.
It is at equilibrium
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Solution
A positive enthalpy change indicates that the reaction absorbs heat, thus it is endothermic.
Correct Answer: B — It is endothermic
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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
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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
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Q. The enthalpy of vaporization of water is approximately ____ kJ/mol.
A.
40.79
B.
60.79
C.
80.79
D.
100.79
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Solution
The enthalpy of vaporization of water is approximately 40.79 kJ/mol.
Correct Answer: A — 40.79
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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
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Solution
The enthalpy of vaporization of water is approximately 2260 kJ/mol.
Correct Answer: B — 2260 kJ/mol
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Q. The entropy change for a phase transition at constant temperature is given by:
A.
ΔS = ΔH/T
B.
ΔS = T/ΔH
C.
ΔS = ΔH*T
D.
ΔS = ΔH + T
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Solution
For a phase transition at constant temperature, the change in entropy is given by ΔS = ΔH/T, where ΔH is the enthalpy change.
Correct Answer: A — ΔS = ΔH/T
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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
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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)
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Q. The entropy of a perfect crystal at absolute zero is given by:
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Solution
According to the third law of thermodynamics, the entropy of a perfect crystal at absolute zero is zero.
Correct Answer: B — 0
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Q. The entropy of a perfect crystal at absolute zero is:
A.
Maximum
B.
Minimum
C.
Undefined
D.
Infinite
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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
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Q. The entropy of a perfect crystal at absolute zero temperature 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
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Solution
The third law of thermodynamics states that the entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.
Correct Answer: A — Third law of thermodynamics
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Q. The entropy of a perfect crystal at absolute zero temperature is given by:
A.
0
B.
1
C.
Infinity
D.
Depends on the substance
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Solution
According to the third law of thermodynamics, the entropy of a perfect crystal at absolute zero is exactly zero.
Correct Answer: A — 0
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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
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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
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Q. The entropy of a perfect crystalline substance at absolute zero is:
A.
Zero
B.
Maximum
C.
Undefined
D.
Infinite
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Solution
According to the third law of thermodynamics, the entropy of a perfect crystalline substance at absolute zero is zero.
Correct Answer: A — Zero
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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
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Solution
The Freundlich isotherm can describe both physisorption and chemisorption processes.
Correct Answer: C — Both physisorption and chemisorption
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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
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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
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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
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Solution
The Langmuir isotherm assumes that adsorption sites are equivalent and that the process is monolayer.
Correct Answer: B — Adsorption sites are equivalent
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Q. The Langmuir adsorption isotherm assumes which of the following?
A.
Adsorption occurs on a surface with infinite sites
B.
Adsorption sites are equivalent
C.
Adsorption is a multilayer process
D.
Adsorption is temperature independent
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Solution
The Langmuir isotherm assumes that adsorption occurs on a surface with a finite number of equivalent sites.
Correct Answer: B — Adsorption sites are equivalent
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Q. The Langmuir isotherm assumes that adsorption occurs at specific sites on the adsorbent. What is the maximum number of molecules that can be adsorbed at a given temperature called?
A.
Adsorption capacity
B.
Saturation capacity
C.
Equilibrium constant
D.
Adsorption energy
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Solution
The maximum number of molecules that can be adsorbed at a given temperature is referred to as the saturation capacity.
Correct Answer: B — Saturation capacity
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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
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Solution
Surface tension arises from cohesive forces between liquid molecules.
Correct Answer: A — Cohesive forces
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Q. The quadratic equation x^2 + 4x + k = 0 has roots that are both negative. What is the condition on k?
A.
k < 0
B.
k > 0
C.
k < 4
D.
k > 4
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Solution
For both roots to be negative, the sum of roots (4) must be positive and the product (k) must be positive, hence k > 0.
Correct Answer: C — k < 4
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Q. The quadratic equation x^2 - 6x + k = 0 has roots that are both positive. What is the condition on k?
A.
k > 0
B.
k < 0
C.
k > 9
D.
k < 9
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Solution
For both roots to be positive, k must be greater than the square of half the coefficient of x: k > (6/2)^2 = 9.
Correct Answer: C — k > 9
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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
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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
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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
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Solution
The rate law for a reaction depends on the mechanism of the reaction.
Correct Answer: C — It depends on the mechanism
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Q. The rate law for a reaction is given as rate = k[A][B]². What is the overall order of the reaction?
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Solution
The overall order of the reaction is the sum of the powers of the concentration terms, which is 1 + 2 = 3.
Correct Answer: C — 3
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Q. The rate of a reaction doubles when the temperature is increased by 10°C. This is an example of which rule?
A.
Arrhenius equation
B.
Van 't Hoff rule
C.
Le Chatelier's principle
D.
Gibbs free energy
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Solution
This is an example of Van 't Hoff rule, which states that the rate of reaction doubles for every 10°C increase in temperature.
Correct Answer: B — Van 't Hoff rule
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Q. The rate of a reaction is defined as the change in concentration of a reactant or product per unit time. What is the unit of rate?
A.
mol/L
B.
mol/L·s
C.
L/mol·s
D.
1/s
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Solution
The rate of reaction is expressed in terms of concentration change per unit time, hence the unit is mol/L·s.
Correct Answer: B — mol/L·s
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Q. The rate of a reaction is directly proportional to the product of the concentrations of the reactants raised to their respective powers. This is known as what?
A.
Rate law
B.
Equilibrium constant
C.
Reaction quotient
D.
Catalytic law
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Solution
This relationship is known as the rate law of the reaction.
Correct Answer: A — Rate law
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Q. The roots of the equation 2x^2 - 4x + k = 0 are 1 and 2. Find the value of k.
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Solution
Using Vieta's formulas, sum of roots = 1 + 2 = 3 = -(-4)/2 => k = 2*1*2 = 4.
Correct Answer: C — 6
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Q. What does a large negative value of ΔG indicate about a reaction?
A.
The reaction is highly spontaneous.
B.
The reaction is non-spontaneous.
C.
The reaction is at equilibrium.
D.
The reaction requires a catalyst.
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Solution
A large negative value of ΔG indicates that the reaction is highly spontaneous and favors the formation of products.
Correct Answer: A — The reaction is highly spontaneous.
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Q. What does a negative ΔG indicate about a chemical reaction?
A.
The reaction is at equilibrium.
B.
The reaction is non-spontaneous.
C.
The reaction is spontaneous.
D.
The reaction requires energy input.
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Solution
A negative ΔG indicates that the reaction is spontaneous under the given conditions.
Correct Answer: C — The reaction is spontaneous.
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