Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

19. Chemical Thermodynamics

Spontaneous vs Nonspontaneous Reactions

General Chemistry

19. Chemical Thermodynamics

Spontaneous vs Nonspontaneous Reactions

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Multiple Choice

The following reaction is spontaneous at room temperature: C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g). Which of the following is true about the enthalpy (ΔH) and entropy (ΔS) changes for this reaction?

ΔH is negative and ΔS is positive

ΔH is negative and ΔS is negative

ΔH is positive and ΔS is negative

ΔH is positive and ΔS is positive

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Verified step by step guidance

Step 1: Understand the concept of spontaneity in chemical reactions. A spontaneous reaction is one that occurs naturally under given conditions without external influence. For a reaction to be spontaneous at room temperature, the Gibbs free energy change (ΔG) must be negative.

Step 2: Recall the Gibbs free energy equation: ΔG = ΔH - TΔS, where ΔG is the change in Gibbs free energy, ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. For a reaction to be spontaneous, ΔG should be negative.

Step 3: Analyze the enthalpy change (ΔH). In combustion reactions like the one given, energy is released as heat, indicating that the reaction is exothermic. Therefore, ΔH is negative.

Step 4: Consider the entropy change (ΔS). Entropy is a measure of disorder or randomness. In the given reaction, the number of gas molecules increases from 6 (1 C3H8 + 5 O2) to 7 (3 CO2 + 4 H2O), suggesting an increase in disorder. Thus, ΔS is positive.

Step 5: Conclude based on the analysis: For the reaction to be spontaneous, ΔH is negative (exothermic) and ΔS is positive (increase in disorder), which aligns with the condition for a negative ΔG.