# Worksheet: The Second Law of Thermodynamics

In this worksheet, we will practice defining the second law of thermodynamics, which states that the entropy of the universe must increase.

Q1:

Which of the following represents a necessary condition for a chemical reaction to proceed from reactants to products spontaneously?

• AThe reaction must be exothermic.
• BThe total entropy of the reacting chemical system and its surroundings must increase.
• CThe reaction must be endothermic.
• DThe standard entropy change, , for the chemical reaction must be ≥ 0.

Q2:

Which of the following played a significant role in developing the concept of entropy and in formulating the second law of thermodynamics?

• AThe Nernst heat theorem
• BThe equipartition of energy principle
• CThe Heisenberg uncertainty principle
• DThe formulation and analysis of the Carnot cycle and heat engine

Q3:

Which of the following statements does not conform to the laws of thermodynamics?

• AThe entropy of any chemically pure substance approaches a value of zero as the temperature of the substance approaches a value of 0 K and at and .
• BThe entropy of a system always decreases with a decrease in the temperature of the system.
• CThe entropy of the universe always increases in a spontaneous change of state process.
• DThe energy of the universe always remains constant in any change of state process.

Q4:

In which of the following processes is the change in the entropy of the system most negative?

• A
• B
• C
• D
• E

Q5:

In which of the following processes is there a decrease in the entropy of the materials involved?

• AOxidation of iron in air
• BCombustion of butane
• CDecomposition of hydrogen peroxide into water and oxygen
• DBoiling of ethanol
• EWarming of ice to near its melting point

Q6:

Why is it difficult to predict whether the entropy change in the complete combustion of methane will be positive or negative?

• AThe products of the reaction vary depending on the oxygen concentration.
• BThe reactants and products can all be modeled as ideal gases.
• CThe reaction does not change the number of covalent bonds.
• DHeat released by the reaction may reverse the sign of the entropy change.
• EThe reaction does not change the number of gaseous molecules.

Q7:

The melting of ice is represented by the equation The standard molar entropy change for this process is 22.1 J/K⋅mol and each mole of water absorbs 6.012 kJ from the surroundings. Calculate the change in the entropy of the universe when 1.00 mole of ice melts at .

Q8:

The boiling of water is represented by the equation The standard molar entropy of a material, , is the molar entropy of the material at 298 K and 1.00 bar pressure. The value of for liquid water is 70.0 J/mol⋅K and the value for steam is 188.8 J/mol⋅K. Calculate , the standard molar entropy change for boiling water.