Ch 18 Free Energy and Thermodynamics Module 1

Which of the following is/are always spontaneous? 

• I only

• II only

• both are always spontaneous

• neither are always spontaneous

The standard molar entropy of lead(II) bromide (PbBr₂) is 161 J/mol ⋅ K. What is the entropy of 2.45 g of PbBr₂?

• +1.07 J/K

• −1.07 J/K

• +161 J/K

• −161 J/K

• 0 J/K

Which of the following processes is predicted to decrease the entropy of a system?

• The number of particles increases.

• Temperature increases.

• Volume increases.

• Pressure increases.

• All of these increase the entropy of the system.

Which of the following will have the greatest standard molar entropy (S°)?

• Cl₂(g)

• Ne(g)

• Na(s)

• CH₃OH(l)

• Na₂CO₃(s)

Which of the following are listed in order of increasing standard molar entropy?

• Au(s) < Au(g) < H₂O(l) < CH₃OH(l) < H₂O(g)

• Au(s) < H₂O(l) < CH₃OH(l) < Au(g) < H₂O(g)

• Au(s) < H₂O(l) < CH₃OH(l) < H₂O(g) < Au(g)

• 
  H₂O(l) < CH₃OH(l) < Au(s) < Au(g) < H₂O(g)

• H₂O(l) < Au(s) < CH₃OH(l) < H₂O(g) < Au(g)

During a spontaneous chemical reaction, it is found that ΔS_sys is less than 0. This means that

• ΔS_surr is less than 0 and its magnitude is less than ΔS_sys.

• ΔS_surr is less than 0 and its magnitude is greater than ΔS_sys.

• ΔS_surr is greater than 0 and its magnitude is less than ΔS_sys.

• ΔS_surr is greater than 0 and its magnitude is greater than ΔS_sys.

• an error has been made, as S_sys is greater than 0 by necessity for a spontaneous process.

Determine ΔS° for the reaction D given the following information.

Substance S° (J/mol ⋅ K)

Fe₂O₃(s) 87.4

Fe(s) 27.3

O₂(g) 205.0

• −144.9 J/mol ⋅ K

• −549.4 J/mol ⋅ K

• +899.0 J/mol ⋅ K

• +549.4 J/mol ⋅ K

• +144.9 J/mol ⋅ K

Determine ΔS° for the reaction D given the following information.  (Your answer should be in units of J/K)

Three significant figures in your answer.

Substance S° (J/mol ⋅ K)

N₂O₄(g) 304.3 

NO₂(g) 240.45

Indicate which of the following reactions results in a negative ΔS_sys.

• 
• 
• 
• 
• 

Indicate which of the following reactions results in a positive ΔS_sys.

• 
• 
• 
• 
•