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Energy Concepts in Thermochemistry Quiz

#1

Which law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another?

First law
Explanation

Conservation of energy principle

#2

What is the SI unit of energy?

Joule
Explanation

Standard unit of energy

#3

Which term refers to the energy required to raise the temperature of one gram of a substance by one degree Celsius?

Specific heat
Explanation

Heat capacity per unit mass

#4

In an exothermic reaction, what happens to the enthalpy change (ΔH)?

It decreases
Explanation

Enthalpy is released

#5

Which term describes the total energy content of a system?

Internal energy
Explanation

Sum of kinetic and potential energies

#6

What is the standard state for enthalpy of formation?

1 atm pressure and 25°C temperature
Explanation

Reference conditions for formation enthalpy

#7

Which of the following statements is true regarding an endothermic reaction?

It absorbs heat from the surroundings
Explanation

Heat absorption

#8

What does a negative value of Gibbs free energy (∆G) indicate for a reaction?

The reaction is spontaneous
Explanation

Spontaneous reaction

#9

Which of the following statements about Hess's Law is true?

It allows the calculation of the overall enthalpy change for a reaction by summing the enthalpy changes for each step of the reaction
Explanation

Summation of enthalpies

#10

Which law of thermodynamics defines absolute zero as the point where entropy is at a minimum?

Third law
Explanation

Entropy at absolute zero

#11

What is the relationship between the standard enthalpy change (∆H°) and the standard internal energy change (∆U°) for a reaction at constant pressure?

∆H° = ∆U° + P∆V
Explanation

Enthalpy and internal energy relationship

#12

Which quantity represents the maximum amount of useful work that can be obtained from a system at constant temperature and pressure?

Gibbs free energy
Explanation

Energy available for work

#13

Which of the following is NOT a state function?

Work
Explanation

Path-dependent quantity

#14

What is the relationship between the standard enthalpy of reaction (∆H°) and the heat of reaction (∆H) at non-standard conditions?

∆H° = ∆H + nRTln(Q)
Explanation

Enthalpy at non-standard conditions

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