Q. How does increasing temperature generally affect the enthalpy of a system?
A.
It decreases the enthalpy
B.
It has no effect on enthalpy
C.
It increases the enthalpy
D.
It depends on the type of reaction
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Solution
Increasing temperature typically increases the enthalpy of a system due to the increased kinetic energy of the molecules.
Correct Answer:
C
— It increases the enthalpy
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Q. In a calorimetry experiment, what does a positive q value indicate?
A.
Heat is released by the system
B.
Heat is absorbed by the system
C.
No heat exchange occurs
D.
The system is at equilibrium
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Solution
A positive q value indicates that the system absorbs heat from the surroundings.
Correct Answer:
B
— Heat is absorbed by the system
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Q. In a chemical reaction, if the enthalpy change (ΔH) is negative, what does this indicate?
A.
The reaction is endothermic
B.
The reaction is exothermic
C.
The reaction is at equilibrium
D.
The reaction requires energy input
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Solution
A negative ΔH indicates that the reaction releases heat to the surroundings, classifying it as exothermic.
Correct Answer:
B
— The reaction is exothermic
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Q. What is the effect of a catalyst on the enthalpy change of a reaction?
A.
Increases the enthalpy change
B.
Decreases the enthalpy change
C.
Has no effect on the enthalpy change
D.
Reverses the enthalpy change
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Solution
A catalyst speeds up the reaction rate without affecting the overall enthalpy change of the reaction.
Correct Answer:
C
— Has no effect on the enthalpy change
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Q. What is the primary purpose of using enthalpy in thermodynamics?
A.
To measure the temperature of a system
B.
To calculate the work done by a system
C.
To determine the heat content of a system at constant pressure
D.
To evaluate the change in volume of a system
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Solution
Enthalpy is defined as the total heat content of a system at constant pressure, making it essential for calculating heat transfer in chemical reactions.
Correct Answer:
C
— To determine the heat content of a system at constant pressure
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Q. What is the relationship between enthalpy change and the spontaneity of a reaction?
A.
A negative enthalpy change guarantees spontaneity
B.
A positive enthalpy change guarantees spontaneity
C.
Enthalpy change does not affect spontaneity
D.
Spontaneity depends on enthalpy and entropy changes
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Solution
Spontaneity is determined by both enthalpy and entropy changes, as described by the Gibbs free energy equation.
Correct Answer:
D
— Spontaneity depends on enthalpy and entropy changes
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Q. What is the standard enthalpy of formation (ΔHf°) for an element in its standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
The same as its molar mass
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Solution
The standard enthalpy of formation for any element in its standard state is defined as zero.
Correct Answer:
A
— 0 kJ/mol
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Q. Which law of thermodynamics states that energy cannot be created or destroyed?
A.
First Law
B.
Second Law
C.
Third Law
D.
Zeroth Law
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Solution
The First Law of Thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed.
Correct Answer:
A
— First Law
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Q. Which of the following is a real-world application of enthalpy calculations?
A.
Designing refrigeration systems
B.
Calculating the pH of solutions
C.
Determining reaction rates
D.
Measuring electrical conductivity
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Solution
Enthalpy calculations are crucial in designing refrigeration systems to ensure efficient heat transfer.
Correct Answer:
A
— Designing refrigeration systems
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Q. Which of the following processes is an example of an endothermic reaction?
A.
Combustion of gasoline
B.
Dissolving ammonium nitrate in water
C.
Formation of water from hydrogen and oxygen
D.
Respiration in living organisms
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Solution
Dissolving ammonium nitrate in water absorbs heat from the surroundings, making it an endothermic process.
Correct Answer:
B
— Dissolving ammonium nitrate in water
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