CHM 2046 General Chemistry 2 Exam 2
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which statement best describes the principal distinction between an
extensive and an intensive thermodynamic property of a chemical system?
A. An extensive property is independent of the amount of matter, whereas
an intensive property depends on the amount of matter.
B. An extensive property depends on the amount of matter, whereas an
intensive property is independent of the amount of matter.
C. Both extensive and intensive properties depend directly on the amount of
matter present.
D. Intensive properties can be measured only for gases, whereas extensive
properties can be measured only for liquids and solids.
Answer: B. An extensive property depends on the amount of matter,
whereas an intensive property is independent of the amount of matter.
Extensive properties, such as mass, volume, and total energy, change when
the quantity of matter changes, while intensive properties, such as
temperature, pressure, and density, do not depend on the amount of
material present.
1. A chemical system absorbs 250 J of heat from its surroundings while
performing 100 J of work on the surroundings. According to the first
law of thermodynamics, what is the change in the internal energy of
the system?
A. +350 J
, B. +150 J
C. −150 J
D. −350 J
Answer: B. +150 J
Using ΔE = q + w, heat absorbed gives q = +250 J and work performed
by the system gives w = −100 J, so ΔE = +250 J − 100 J = +150 J.
2. Which situation represents an exothermic chemical process?
A. The system absorbs heat and the surroundings become cooler.
B. The system releases heat and the surroundings become warmer.
C. The system absorbs heat while its enthalpy decreases.
D. The system undergoes expansion without any heat transfer.
Answer: B. The system releases heat and the surroundings become
warmer.
An exothermic process releases heat from the system to the
surroundings, so the system has a negative enthalpy change under
constant-pressure conditions and the surroundings gain thermal
energy.
3. Which mathematical expression correctly defines the enthalpy change
for a reaction?
A. ΔH = Hreactants − Hproducts
B. ΔH = Hproducts − Hreactants
C. ΔH = Hproducts + Hreactants
D. ΔH = Hreactants/Hproducts
Answer: B. ΔH = Hproducts − Hreactants
Enthalpy change is calculated by subtracting the enthalpy of the
reactants from that of the products, so a negative value indicates an
exothermic reaction and a positive value indicates an endothermic
reaction.
ΔH=Hproducts−Hreactants
ΔH=−50 kJ\Delta H=−50\,\mathrm{kJ}ΔH=−50kJExothermic example · Heat
out
ΔH\Delta HΔH
-5
kJ
,ΔH\Delta HΔH
Exothermic example
246810100Reaction directionRelative energyReactantsProductsE_a
Give feedback
5. A reaction has ΔH = −285.8 kJ. Which interpretation is correct?
A. The reaction absorbs 285.8 kJ per mole of reaction as written.
B. The reaction releases 285.8 kJ per mole of reaction as written.
C. The reaction has no heat transfer because ΔH is negative.
D. The reaction must be nonspontaneous because ΔH is negative.
Answer: B. The reaction releases 285.8 kJ per mole of reaction as
written.
A negative enthalpy change means the products have lower enthalpy
than the reactants, and the difference is released as heat to the
surroundings at constant pressure.
6. Which statement correctly describes Hess's law?
A. The enthalpy change depends on the reaction mechanism used.
B. The enthalpy change depends only on the initial and final states,
regardless of the pathway.
C. The enthalpy change is always positive for multistep reactions.
D. The enthalpy change can be determined only experimentally.
Answer: B. The enthalpy change depends only on the initial and final
states, regardless of the pathway.
Because enthalpy is a state function, the overall enthalpy change is
independent of the pathway and can be calculated by adding the
enthalpy changes of appropriate intermediate reactions.
7. Given the reactions C(s) + O₂(g) → CO₂(g), ΔH = −393.5 kJ, and CO(g) +
½O₂(g) → CO₂(g), ΔH = −283.0 kJ, what is ΔH for C(s) + ½O₂(g) →
CO(g)?
A. −676.5 kJ
B. −110.5 kJ
C. +110.5 kJ
D. +676.5 kJ
Answer: B. −110.5 kJ
Reversing the second equation gives ΔH = +283.0 kJ, and adding it to
, the first equation gives −393.5 + 283.0 = −110.5 kJ for formation of
CO.
8. Which quantity is directly related to the heat transferred during a
process carried out at constant pressure when only pressure-volume
work occurs?
A. Internal energy change
B. Enthalpy change
C. Entropy change only
D. Gibbs free energy change only
Answer: B. Enthalpy change
At constant pressure, with only pressure-volume work, the heat
absorbed or released by the system is equal to its enthalpy change,
qₚ = ΔH.
9. A 50.0-g sample of water is heated from 20.0°C to 35.0°C. If the
specific heat capacity of water is 4.184 J g⁻¹ °C⁻¹, how much heat is
absorbed?
A. 313.8 J
B. 418.4 J
C. 3,138 J
D. 4,184 J
Answer: C. 3,138 J
Using q = mcΔT gives q = (50.0 g)(4.184 J g⁻¹ °C⁻¹)(15.0°C) = 3.138 ×
10³ J.
ΔT=mcq
Water: 20°C → 29.6°C after 40 kJ.
Sample
CopperSandWater
CopperSandWater
Heat
40
kJ
Heat
Before heating
After heating
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. Which statement best describes the principal distinction between an
extensive and an intensive thermodynamic property of a chemical system?
A. An extensive property is independent of the amount of matter, whereas
an intensive property depends on the amount of matter.
B. An extensive property depends on the amount of matter, whereas an
intensive property is independent of the amount of matter.
C. Both extensive and intensive properties depend directly on the amount of
matter present.
D. Intensive properties can be measured only for gases, whereas extensive
properties can be measured only for liquids and solids.
Answer: B. An extensive property depends on the amount of matter,
whereas an intensive property is independent of the amount of matter.
Extensive properties, such as mass, volume, and total energy, change when
the quantity of matter changes, while intensive properties, such as
temperature, pressure, and density, do not depend on the amount of
material present.
1. A chemical system absorbs 250 J of heat from its surroundings while
performing 100 J of work on the surroundings. According to the first
law of thermodynamics, what is the change in the internal energy of
the system?
A. +350 J
, B. +150 J
C. −150 J
D. −350 J
Answer: B. +150 J
Using ΔE = q + w, heat absorbed gives q = +250 J and work performed
by the system gives w = −100 J, so ΔE = +250 J − 100 J = +150 J.
2. Which situation represents an exothermic chemical process?
A. The system absorbs heat and the surroundings become cooler.
B. The system releases heat and the surroundings become warmer.
C. The system absorbs heat while its enthalpy decreases.
D. The system undergoes expansion without any heat transfer.
Answer: B. The system releases heat and the surroundings become
warmer.
An exothermic process releases heat from the system to the
surroundings, so the system has a negative enthalpy change under
constant-pressure conditions and the surroundings gain thermal
energy.
3. Which mathematical expression correctly defines the enthalpy change
for a reaction?
A. ΔH = Hreactants − Hproducts
B. ΔH = Hproducts − Hreactants
C. ΔH = Hproducts + Hreactants
D. ΔH = Hreactants/Hproducts
Answer: B. ΔH = Hproducts − Hreactants
Enthalpy change is calculated by subtracting the enthalpy of the
reactants from that of the products, so a negative value indicates an
exothermic reaction and a positive value indicates an endothermic
reaction.
ΔH=Hproducts−Hreactants
ΔH=−50 kJ\Delta H=−50\,\mathrm{kJ}ΔH=−50kJExothermic example · Heat
out
ΔH\Delta HΔH
-5
kJ
,ΔH\Delta HΔH
Exothermic example
246810100Reaction directionRelative energyReactantsProductsE_a
Give feedback
5. A reaction has ΔH = −285.8 kJ. Which interpretation is correct?
A. The reaction absorbs 285.8 kJ per mole of reaction as written.
B. The reaction releases 285.8 kJ per mole of reaction as written.
C. The reaction has no heat transfer because ΔH is negative.
D. The reaction must be nonspontaneous because ΔH is negative.
Answer: B. The reaction releases 285.8 kJ per mole of reaction as
written.
A negative enthalpy change means the products have lower enthalpy
than the reactants, and the difference is released as heat to the
surroundings at constant pressure.
6. Which statement correctly describes Hess's law?
A. The enthalpy change depends on the reaction mechanism used.
B. The enthalpy change depends only on the initial and final states,
regardless of the pathway.
C. The enthalpy change is always positive for multistep reactions.
D. The enthalpy change can be determined only experimentally.
Answer: B. The enthalpy change depends only on the initial and final
states, regardless of the pathway.
Because enthalpy is a state function, the overall enthalpy change is
independent of the pathway and can be calculated by adding the
enthalpy changes of appropriate intermediate reactions.
7. Given the reactions C(s) + O₂(g) → CO₂(g), ΔH = −393.5 kJ, and CO(g) +
½O₂(g) → CO₂(g), ΔH = −283.0 kJ, what is ΔH for C(s) + ½O₂(g) →
CO(g)?
A. −676.5 kJ
B. −110.5 kJ
C. +110.5 kJ
D. +676.5 kJ
Answer: B. −110.5 kJ
Reversing the second equation gives ΔH = +283.0 kJ, and adding it to
, the first equation gives −393.5 + 283.0 = −110.5 kJ for formation of
CO.
8. Which quantity is directly related to the heat transferred during a
process carried out at constant pressure when only pressure-volume
work occurs?
A. Internal energy change
B. Enthalpy change
C. Entropy change only
D. Gibbs free energy change only
Answer: B. Enthalpy change
At constant pressure, with only pressure-volume work, the heat
absorbed or released by the system is equal to its enthalpy change,
qₚ = ΔH.
9. A 50.0-g sample of water is heated from 20.0°C to 35.0°C. If the
specific heat capacity of water is 4.184 J g⁻¹ °C⁻¹, how much heat is
absorbed?
A. 313.8 J
B. 418.4 J
C. 3,138 J
D. 4,184 J
Answer: C. 3,138 J
Using q = mcΔT gives q = (50.0 g)(4.184 J g⁻¹ °C⁻¹)(15.0°C) = 3.138 ×
10³ J.
ΔT=mcq
Water: 20°C → 29.6°C after 40 kJ.
Sample
CopperSandWater
CopperSandWater
Heat
40
kJ
Heat
Before heating
After heating
