Multiple Choice
For a reaction to be spontaneous at all temperatures, the signs of ΔH and ΔS must be:
19. Chemical Thermodynamics
Spontaneous vs Nonspontaneous Reactions
Struggling with General Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
The process of iron being oxidized to make iron(III) oxide (rust) is spontaneous. Which of these statements about this process is true?
A
The reduction of iron(III) oxide to iron is also spontaneous.
B
The oxidation of iron is an endothermic process.
C
Because the process is spontaneous, the oxidation of iron leads to a decrease in Gibbs free energy.
D
The formation of rust is a nonspontaneous process under standard conditions.
Verified step by step guidance1
Understand the concept of spontaneity in chemical reactions: A spontaneous process is one that occurs naturally under given conditions without external intervention. It is often associated with a decrease in Gibbs free energy (ΔG).
Recall the relationship between Gibbs free energy and spontaneity: For a process to be spontaneous, the change in Gibbs free energy (ΔG) must be negative. This indicates that the system is releasing energy and moving towards a more stable state.
Consider the oxidation of iron to form iron(III) oxide: This is a spontaneous process, meaning ΔG < 0. Therefore, the statement 'Because the process is spontaneous, the oxidation of iron leads to a decrease in Gibbs free energy' is true.
Evaluate the other statements: The reduction of iron(III) oxide to iron is not spontaneous under the same conditions because it would require an input of energy, making ΔG > 0. The oxidation of iron is not endothermic; it is exothermic, releasing energy as heat.
Understand the conditions for spontaneity: The formation of rust is spontaneous under standard conditions, contradicting the statement 'The formation of rust is a nonspontaneous process under standard conditions.'
4:20mWatch next
Master Spontaneity of Processes with a bite sized video explanation from Jules
Start learningRelated Videos
Related Practice
Spontaneous vs Nonspontaneous Reactions practice set
Problem sets built by lead tutorsExpert video explanations