Q. What is the standard enthalpy change for the reaction 2H2(g) + O2(g) → 2H2O(l)?
A.
-285.83 kJ/mol
B.
-241.82 kJ/mol
C.
-572.4 kJ/mol
D.
-1000 kJ/mol
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Solution
The standard enthalpy of formation of water is -241.82 kJ/mol.
Correct Answer: B — -241.82 kJ/mol
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Q. What is the standard enthalpy change for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) if ΔHf°(NH3) = -45.9 kJ/mol?
A.
-91.8 kJ
B.
0 kJ
C.
45.9 kJ
D.
91.8 kJ
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Solution
ΔH = 2 * ΔHf°(NH3) = 2 * (-45.9) = -91.8 kJ
Correct Answer: A — -91.8 kJ
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Q. What is the standard enthalpy change for the reaction: C(s) + O2(g) → CO2(g) if ΔHf° for CO2 is -393.5 kJ/mol?
A.
-393.5 kJ
B.
0 kJ
C.
393.5 kJ
D.
None of the above
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Solution
The standard enthalpy change is equal to the enthalpy of formation of CO2, which is -393.5 kJ.
Correct Answer: A — -393.5 kJ
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Q. What is the standard enthalpy change of formation for a substance?
A.
The enthalpy change when one mole of a compound is formed from its elements in their standard states.
B.
The enthalpy change when one mole of a substance is completely burned in oxygen.
C.
The enthalpy change when one mole of a substance is dissolved in water.
D.
The enthalpy change when one mole of a gas is compressed to a smaller volume.
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Solution
The standard enthalpy change of formation is defined as the enthalpy change when one mole of a compound is formed from its elements in their standard states.
Correct Answer: A — The enthalpy change when one mole of a compound is formed from its elements in their standard states.
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Q. What is the standard enthalpy change of formation for an element in its standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy change of formation for an element in its standard state is defined as 0 kJ/mol.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard enthalpy change of formation for elements in their standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy change of formation for elements in their standard state is defined as zero.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard enthalpy change of formation for water (H2O) at 25°C?
A.
-285.83 kJ/mol
B.
-241.82 kJ/mol
C.
-393.5 kJ/mol
D.
-241.0 kJ/mol
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Solution
The standard enthalpy change of formation for water at 25°C is -241.82 kJ/mol.
Correct Answer: B — -241.82 kJ/mol
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Q. What is the standard enthalpy of formation for an element in its standard state?
A.
0 kJ/mol
B.
100 kJ/mol
C.
298 kJ/mol
D.
1 kJ/mol
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Solution
The standard enthalpy of formation for an element in its standard state is defined as 0 kJ/mol.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard enthalpy of formation for elements in their standard state?
A.
0 kJ/mol
B.
1 kJ/mol
C.
100 kJ/mol
D.
Not defined
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Solution
The standard enthalpy of formation for elements in their standard state is defined as 0 kJ/mol.
Correct Answer: A — 0 kJ/mol
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Q. What is the standard entropy change (ΔS°) for the reaction: 2 SO2(g) + O2(g) → 2 SO3(g)?
A.
Positive
B.
Negative
C.
Zero
D.
Cannot be determined
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Solution
The reaction decreases the number of gas molecules from 3 to 2, leading to a decrease in disorder and thus a negative ΔS°.
Correct Answer: B — Negative
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Q. What is the standard entropy change (ΔS°) for the reaction: 2H2(g) + O2(g) → 2H2O(g)?
A.
Positive
B.
Negative
C.
Zero
D.
Cannot be determined
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Solution
The reaction results in a decrease in the number of gas molecules (from 3 to 2), leading to a negative change in entropy.
Correct Answer: B — Negative
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Q. What is the standard entropy change (ΔS°) for the reaction: 2SO2(g) + O2(g) → 2SO3(g)?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Cannot be determined
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Solution
The reaction decreases the number of gas molecules from 3 to 2, leading to a decrease in entropy.
Correct Answer: B — Decreases
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Q. What is the standard Gibbs Free Energy change (ΔG°) for a reaction at standard conditions?
A.
Always zero
B.
Depends on the reaction
C.
Is a constant value
D.
Is always positive
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Solution
ΔG° depends on the specific reaction and its conditions.
Correct Answer: B — Depends on the reaction
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Q. What is the standard molar entropy of a substance?
A.
Entropy at 0 K
B.
Entropy at 25 °C and 1 atm
C.
Entropy at boiling point
D.
Entropy at melting point
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Solution
Standard molar entropy is defined as the entropy of 1 mole of a substance at 25 °C and 1 atm pressure.
Correct Answer: B — Entropy at 25 °C and 1 atm
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Q. What is the standard state of a substance?
A.
The most stable form at 1 atm and 25°C
B.
Any form of the substance
C.
The gaseous form only
D.
The liquid form only
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Solution
The standard state of a substance is defined as its most stable form at 1 atm pressure and 25°C.
Correct Answer: A — The most stable form at 1 atm and 25°C
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Q. What is the term for the change of state from gas to liquid?
A.
Sublimation
B.
Condensation
C.
Evaporation
D.
Freezing
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Solution
Condensation is the process where gas turns into liquid as it loses energy.
Correct Answer: B — Condensation
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Q. What is the term for the change of state from liquid to gas?
A.
Condensation
B.
Evaporation
C.
Sublimation
D.
Freezing
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Solution
Evaporation is the process of changing from liquid to gas.
Correct Answer: B — Evaporation
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Q. What is the term for the change of state from solid to gas?
A.
Sublimation
B.
Deposition
C.
Evaporation
D.
Condensation
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Solution
Sublimation is the process where a solid changes directly into a gas.
Correct Answer: A — Sublimation
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Q. What is the term for the energy required to increase the surface area of a liquid?
A.
Viscosity
B.
Surface tension
C.
Cohesion
D.
Adhesion
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Solution
Surface tension is the energy required to increase the surface area of a liquid.
Correct Answer: B — Surface tension
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Q. What is the term for the pressure exerted by a vapor in equilibrium with its liquid?
A.
Saturation pressure
B.
Vapor pressure
C.
Boiling point
D.
Critical pressure
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Solution
Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid.
Correct Answer: B — Vapor pressure
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Q. What is the term for the process by which a liquid changes into a gas?
A.
Condensation
B.
Evaporation
C.
Sublimation
D.
Deposition
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Solution
Evaporation is the process by which a liquid changes into a gas.
Correct Answer: B — Evaporation
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Q. What is the term for the process by which a liquid changes to a gas?
A.
Condensation
B.
Evaporation
C.
Sublimation
D.
Deposition
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Solution
Evaporation is the process by which a liquid changes to a gas.
Correct Answer: B — Evaporation
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Q. What is the term for the process by which a liquid turns into vapor?
A.
Condensation
B.
Evaporation
C.
Sublimation
D.
Deposition
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Solution
Evaporation is the process by which a liquid turns into vapor.
Correct Answer: B — Evaporation
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Q. What is the term for the process of a liquid turning into vapor?
A.
Condensation
B.
Evaporation
C.
Sublimation
D.
Deposition
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Solution
Evaporation is the process by which a liquid turns into vapor.
Correct Answer: B — Evaporation
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Q. What is the term for the process of removing adsorbed molecules from a surface?
A.
Absorption
B.
Desorption
C.
Sorption
D.
Adsorption
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Solution
Desorption is the process of removing adsorbed molecules from a surface.
Correct Answer: B — Desorption
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Q. What is the term for the process where a gas or liquid forms a thin layer on a solid surface?
A.
Absorption
B.
Desorption
C.
Adsorption
D.
Sorption
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Solution
Adsorption is the process where a gas or liquid forms a thin layer on a solid surface.
Correct Answer: C — Adsorption
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Q. What is the term for the resistance of a liquid to flow?
A.
Viscosity
B.
Surface tension
C.
Density
D.
Capillarity
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Solution
Viscosity is the measure of a liquid's resistance to flow.
Correct Answer: A — Viscosity
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Q. What is the term for the temperature at which a liquid turns into vapor?
A.
Melting point
B.
Boiling point
C.
Freezing point
D.
Sublimation point
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Solution
The boiling point is the temperature at which a liquid turns into vapor.
Correct Answer: B — Boiling point
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Q. What is the term for the temperature at which a liquid's vapor pressure equals the external pressure?
A.
Melting point
B.
Freezing point
C.
Boiling point
D.
Critical point
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Solution
The boiling point is defined as the temperature at which a liquid's vapor pressure equals the external pressure.
Correct Answer: C — Boiling point
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Q. What is the term for the temperature at which a solid becomes a liquid?
A.
Boiling point
B.
Melting point
C.
Freezing point
D.
Sublimation point
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Solution
The melting point is the temperature at which a solid becomes a liquid.
Correct Answer: B — Melting point
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