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Thermodynamics vs. kinetics | Applications of thermodynamics | AP Chemistry | Khan Academy
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Thermodynamics vs. kinetics | Applications of thermodynamics | AP Chemistry | Khan Academy

Understanding Thermodynamics and Kinetics in Carbon Conversion

Distinction Between Thermodynamics and Kinetics

  • The tutor emphasizes the importance of distinguishing between thermodynamics (what will happen) and kinetics (when it could happen) in chemical reactions, using the conversion of carbon from diamond to graphite as an example.

Thermodynamic Analysis

  • To determine if the conversion occurs at room temperature (25°C), we calculate the standard change in free energy for the reaction, requiring knowledge of the free energy of formation for both products and reactants.
  • The product, graphite, has a standard change in free energy of formation equal to zero since it is the most stable form of carbon at one atmosphere pressure.
  • The reactant, diamond, has a standard change in free energy of formation valued at 2.84 kJ/mol. This value is used to assess the overall reaction's feasibility.

Calculation Steps

  • For one mole of diamond converting to one mole of graphite, we find that subtracting gives us a negative value (-2.84 kJ), indicating that this reaction is thermodynamically favorable.
  • The calculation confirms that because moles cancel out appropriately, we can express our result as kilojoules per mole of reaction.

Kinetic Considerations

  • Examining diamond's structure reveals each carbon atom bonded tetrahedrally to four others; contrastingly, graphite consists of layers held by weaker London dispersion forces.
  • Converting diamond into graphite requires breaking numerous strong carbon-carbon bonds which demands significant energy input.

Activation Energy and Reaction Rate

  • The high activation energy (EA) associated with this reaction results in a very slow rate; estimates suggest it could take billions of years at room temperature.

Summary Insights

  • In summary: thermodynamics indicates that diamond will convert into graphite at room temperature due to a negative ΔG; however, kinetics reveals that this process would take an impractically long time due to high activation energy.
  • Thus, while thermodynamically favorable, the conversion remains kinetically unfavorable under normal conditions.
Video description

Thermodynamics tells us what can occur during a process, while kinetics tell us what actually occurs. Some processes, such as the conversion of diamond to graphite, are thermodynamically favored but kinetically unfavored. In these cases, the processes do not occur to any measurable extent. View more lessons or practice this subject at https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:applications-of-thermodynamics/x2eef969c74e0d802:thermodynamics-vs-kinetics/v/thermodynamics-vs-kinetics-ap Khan Academy is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We offer quizzes, questions, instructional videos, and articles on a range of academic subjects, including math, biology, chemistry, physics, history, economics, finance, grammar, preschool learning, and more. We provide teachers with tools and data so they can help their students develop the skills, habits, and mindsets for success in school and beyond. Khan Academy has been translated into dozens of languages, and 15 million people around the globe learn on Khan Academy every month. As a 501(c)(3) nonprofit organization, we would love your help! Donate or volunteer today! Donate here: https://www.khanacademy.org/donate?utm_source=youtube&utm_medium=desc Volunteer here: https://www.khanacademy.org/contribute?utm_source=youtube&utm_medium=desc