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WorksheetsQ4 GENCHEM2 REVIEWER
Total questions: 50
Worksheet time: 25mins
What type of energy change occurs when a reaction absorbs heat from its surroundings?
Chemical
Endothermic
Exothermic
Physical
What is the main energy change in an endothermic reaction?
Energy is absorbed from the surroundings
Energy is released as heat
No energy change occurs
Energy is converted into sound
During an exothermic reaction, energy is primarily released in what form?
Heat
Light
Sound
Work
What form of energy is often released in an exothermic reaction?
Electrical energy
Light and heat energy
Sound energy
Nuclear energy
The First Law of Thermodynamics is essentially a statement of what fundamental principle?
Entropy increase
Energy conservation
Heat transfer direction
Equilibrium establishment
In the context of the First Law, what does the term "internal energy" refer to?
Heat transferred into the system only.
External forces applied to the system.
Total energy contained within the system.
Work performed by the system on its surroundings.
In which reaction is heat absorbed from the surroundings?
Respiration
Neutralization
Freezing
Photosynthesis
Which of the following reactions releases energy in the form of heat and light?
Dissolving salt in water
Exploding fireworks
Cooking an egg
Melting ice cream
What does the First Law of Thermodynamics state?
Energy can be created and destroyed
Energy cannot be transferred or converted
Energy cannot be created or destroyed, only transformed
Energy is always lost in any process
What thermodynamic property is defined as the sum of a system's internal energy and the product of its pressure and volume?
Entropy
Enthalpy
Gibbs free energy
Work.
Which of the following best describes the First Law of Thermodynamics?
Heat cannot flow from a colder body to a hotter body
The total energy of an isolated system remains constant
The universe is moving toward disorder
Work done is independent of heat transfer
According to the First Law of Thermodynamics, when work is done on a system, its internal energy:
Increases
Decreases
Remains the same
Always becomes zero
What symbol is commonly used to represent enthalpy?
G
H
S
U
What does entropy (S) measure in a chemical system?
Disorder
Heat content
Reaction speed
Stability
What is the unit of enthalpy?
Joules (J)
Watts (W)
Newtons (N)
Pascals (Pa)
Which equation determines the spontaneity of a chemical reaction?
ΔG=ΔH−TΔS
ΔS=qrev/T
ΔH=Hproducts−Hreactants
PV=nRTPV
What does the Second Law of Thermodynamics imply about energy conversion?
All energy is converted into work.
Some energy is always lost as heat.
Energy transformations have no limits.
Heat engines operate at 100% efficiency.
What is entropy (S)?
The total energy of a system
A measure of disorder or randomness in a system
The heat content of a system
The energy required to start a reaction
What does a high entropy value indicate?
A highly ordered system
A highly disordered system
No energy change
A spontaneous reaction
What is spontaneity in chemical processes?
The rate at which a reaction occurs
The ability of a reaction to occur without external energy input
The amount of energy absorbed in a reaction
The randomness of a system
Which of the following increases entropy (S) in a system?
Freezing water
Melting ice
Formation of a solid from a gas
Compressing a gas
How does an increase in entropy affect spontaneity?
It always makes a reaction non-spontaneous
It has no effect on spontaneity
It tends to make a reaction more spontaneous
It always stops the reaction
What fundamental concept does the Second Law of Thermodynamics reinforce?
Conservation of mass
Creation of energy
Increase of entropy
Reversibility of processes
Which equation correctly represents Gibbs free energy?
ΔG = ΔH + TΔS
ΔG = ΔH - TΔS
ΔG = ΔS - TΔH
ΔG = TΔH - ΔS
Which of the following factors determines the spontaneity of a reaction?
Only enthalpy change (ΔH)
Only entropy change (ΔS)
The Gibbs free energy change (ΔG)
The activation energy
What does a negative ΔH indicate?
The reaction is exothermic
The reaction is endothermic
The reaction is at equilibrium
The reaction absorbs energy
Chemical equilibrium is a dynamic process. What does "dynamic" mean in this context?
Reactions completely stop
Only the forward reaction happens
Only the reverse reaction happens
The forward and reverse reactions continue occurring
What is the term for the ratio of product concentrations to reactant concentrations at equilibrium?
Activation energy.
Equilibrium constant.
Reaction rate.
Standard enthalpy.
A scientist observes a chemical reaction at equilibrium. When the temperature is increased, the system shifts to counteract this change. What principle explains this behavior?
Boyle's Law
Hess's Law
Le Chatelier's Principle
The Law of Conservation of Mass
When is a reaction always non-spontaneous?
When ΔH is negative and ΔS is positive
When ΔH is positive and ΔS is negative
When ΔG is negative
When the reaction is exothermic
How does entropy change affect the spontaneity of a reaction at low temperatures?
Entropy has a stronger effect than enthalpy
Enthalpy dominates in determining spontaneity
Spontaneity depends only on entropy
The reaction is always spontaneous
Le Chatelier's Principle states that when a system at equilibrium is disturbed, it will:
Remain unchanged
Stop reacting completely
Change its equilibrium constant
Shift in a direction that minimizes the disturbance
Why is the condensation of water vapor considered an exothermic process?
It involves no change in energy.
It releases heat to the surroundings.
It maintains a constant temperature.
It absorbs heat from the surroundings.
In which scenario does the system's enthalpy increase, indicating an endothermic reaction?
A metal rusting in the presence of oxygen.
A burning candle produces light and heat.
The explosion of dynamite releasing gases and heat.
Photosynthesis in plants converting light into glucose.
How does the First Law of Thermodynamics explain the conservation of energy in a closed system?
Energy is lost to the surroundings
Energy is created within the system
Energy is destroyed within the system
Energy is transformed but remains constant
Which best explains the mathematical form of the First Law of Thermodynamics, ΔU = Q - W?
Work and heat increase energy
Energy is destroyed when work is done
Work and heat have no effect on energy
Internal energy changes by heat and work
If K>1, what does it indicate about the equilibrium position?
Reactants are favored
Products are favored
Reaction is non-spontaneous
Reaction is at initial state
If a reaction has a negative enthalpy change (ΔHrxn<0), what can be concluded about the reaction?
It is exothermic.
It is endothermic.
It is at equilibrium.
It requires a catalyst.
If the equilibrium constant (K) is very small (K<1), it means:
The reaction goes to completion
Reactants are favored at equilibrium
Products are favored at equilibrium
Reaction occurs very fast
Consider a reaction where breaking bonds requires more energy than forming new bonds. What is the sign of ΔHrxn and the nature of the reaction?
ΔHrxn is positive; the reaction is exothermic.
ΔHrxn is positive; the reaction is endothermic.
ΔHrxn is negative; the reaction is exothermic.
ΔHrxn is negative; the reaction is endothermic.
How does an increase in entropy generally affect the spontaneity of a process?
Increases spontaneity.
Decreases spontaneity.
Has no effect on spontaneity.
Reverses the direction of the process.
When is entropy (S) likely to increase in a chemical reaction?
When the temperature decreases
When a solid dissolves in a liquid
When a gas condenses into a liquid
When two gases combine to form a solid
Machines and engines operate by converting heat energy into work. However, according to the Second Law of Thermodynamics, no machine can be perfectly efficient. Why is this true?
Heat cannot be used to do work
Energy is always created during a process
Some energy is always lost as waste heat
The First Law of Thermodynamics prevents efficiency
A hot cup of coffee cools down when left on a table. According to the Second Law of Thermodynamics, why does this happen?
The coffee loses mass as it cools
The total energy of the system decreases
Heat flows from a cooler object to a hotter object
Heat energy spontaneously disperses to the surroundings
A chemist measures the Gibbs free energy change (ΔG) of a reaction and finds it to be -25 kJ/mol. What does this result indicate?
The reaction is exothermic.
The reaction is endothermic.
The reaction is spontaneous.
The reaction is non-spontaneous.
A reaction with ΔG = +45 kJ is observed at standard conditions. What does this indicate about the reaction?
The reaction is at equilibrium
The reaction is spontaneous
The reaction releases energy
The reaction is non-spontaneous
If the rate of the forward reaction suddenly increases in a system at equilibrium, what immediate adjustment will occur?
No change in reverse rate.
The reverse rate increases.
The reverse rate decreases.
Equilibrium shifts to reactants.
A student observes a reaction in equilibrium and notices that the concentrations of reactants and products are unchanged over time. What explains this observation?
The reaction is not reversible
The reactants are completely used up
The forward and reverse reactions stop happening
The rates of the forward and reverse reactions are equal
When the concentration of a product is decreased in a system at equilibrium, how does the system respond?
It favors the reverse reaction.
It favors the forward reaction.
It remains unchanged.
It oscillates indefinitely.
According to Le Chatelier's principle, how does an equilibrium system respond to a disturbance?
By shifting in the direction that counteracts the disturbance
By stopping the reaction completely
By maintaining the same concentrations
By increasing the temperature
