3. The enthalpy for oxidation of diamond by oxygen to carbon dioxide is -395.4 k

Question

3. The enthalpy for oxidation of diamond by oxygen to carbon dioxide is -395.4 kJ/mol but the enthalpy for oxidation of graphite to carbon dioxide is -393.4 kJ/mol. Find the enthalpy of reaction for graphite going to diamond. Is this reaction exothermic or endothermic? What does it imply about the chemical bonding in diamond compared to graphite?

Explanation / Answer

C (s, graphite) + O2(g) ---> CO2(g) ?H° = -393.5 kJ C (s, diamond) + O2(g) ---> CO2(g) ?H° = -395.4 kJ What I am going to do is reverse the bottom equation. This will put the C (s, diamond) on the product side, where we need it. Also, when I add the two equations together, the oxygen and carbon dioxide will cancel out. This is, of course, what we want since those two substances are not in the final, desired equation. Here are the two equations again, with the second one reversed: C (s, graphite) + O2(g) ---> CO2(g) ?H° = -393.5 kJ CO2(g) ---> C (s, diamond) + O2(g) ?H° = +395.4 kJ Now I'm ready to add the equations together. When I do this I also add the enthalpies together. Here is the added equation without anything taken out: CO2(g) + C (s, graphite) + O2(g) ---> CO2(g) + C (s, diamond) + O2(g) ?H° = (-393.5 kJ) + (+395.4 kJ) Notice the items which are the same on both sides and remove them: C (s, graphite) ---> C (s, diamond) ?H° = +1.9 kJ

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.