Q. For an ideal gas, which equation relates the change in internal energy to heat and work?
A.
ΔU = Q + W
B.
ΔU = Q - W
C.
ΔU = W - Q
D.
ΔU = Q * W
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Solution
The first law of thermodynamics states that the change in internal energy (ΔU) is equal to the heat added to the system (Q) minus the work done by the system (W).
Correct Answer:
B
— ΔU = Q - W
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Q. In a closed system, if the volume of a gas is halved while the temperature remains constant, what happens to the pressure?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Boyle's Law, if the volume is halved, the pressure will double (P1V1 = P2V2).
Correct Answer:
A
— It doubles
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Q. In a phase diagram, what does the line between the solid and liquid phases represent?
A.
Sublimation point
B.
Melting point
C.
Boiling point
D.
Triple point
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Solution
The line between the solid and liquid phases in a phase diagram represents the melting point, where solid and liquid coexist.
Correct Answer:
B
— Melting point
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Q. In a reaction at equilibrium, what happens if the concentration of reactants is increased?
A.
The equilibrium shifts to the right
B.
The equilibrium shifts to the left
C.
The equilibrium remains unchanged
D.
The reaction stops
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right, favoring product formation.
Correct Answer:
A
— The equilibrium shifts to the right
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Q. In the context of gas laws, what does the term 'absolute zero' refer to?
A.
0 K
B.
273.15 °C
C.
32 °F
D.
100 °C
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Solution
Absolute zero is defined as 0 Kelvin, the theoretical temperature at which a system's entropy reaches its minimum value.
Correct Answer:
A
— 0 K
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Q. What happens to the vapor pressure of a liquid as temperature increases?
A.
It decreases
B.
It remains constant
C.
It increases
D.
It becomes zero
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Solution
As temperature increases, the kinetic energy of the molecules increases, leading to an increase in vapor pressure.
Correct Answer:
C
— It increases
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Q. What is the primary factor that determines the rate of diffusion of a gas?
A.
Molecular weight
B.
Temperature
C.
Pressure
D.
Volume
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Solution
According to Graham's law of effusion, the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.
Correct Answer:
A
— Molecular weight
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Q. What is the van der Waals equation used for?
A.
Describing ideal gas behavior
B.
Describing real gas behavior
C.
Calculating enthalpy changes
D.
Calculating reaction rates
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Solution
The van der Waals equation accounts for the volume occupied by gas molecules and the attractive forces between them, thus describing real gas behavior.
Correct Answer:
B
— Describing real gas behavior
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Q. Which of the following statements about the ideal gas law is true?
A.
It applies to all gases under all conditions
B.
It is derived from empirical observations
C.
It is only valid at high pressures
D.
It assumes no intermolecular forces
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Solution
The ideal gas law assumes that there are no intermolecular forces between gas particles, which is a key limitation of the model.
Correct Answer:
D
— It assumes no intermolecular forces
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Q. Which of the following statements about the phase diagram of a substance is true?
A.
The triple point is where all three phases coexist
B.
The critical point is where the solid and liquid phases coexist
C.
The vapor pressure curve separates solid and liquid phases
D.
The sublimation curve separates liquid and gas phases
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Solution
The triple point is the unique set of conditions at which all three phases (solid, liquid, gas) coexist in equilibrium.
Correct Answer:
A
— The triple point is where all three phases coexist
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