Hydrogenation of alkenes typically displays DH8 5 230 kcal mol21. Whichof the following

Chapter 11, Problem 1-3

(choose chapter or problem)

Hydrogenation of alkenes typically displays DH8 5 230 kcal mol21. Whichof the following statements are always true? (a) Mixing an alkene with H2 results in a fastreaction; (b) reaction of an alkene with H2 is exothermic; (c) all alkenes react equally favorablywith H2.What? This is a three-part true false question. You must think about each statementindividually.(a) Start: Does energetic (thermodynamic) favorability necessarily determine how fasta reaction will go? Information: No. What does? Remember kinetics? Activation energies(Sections 3-3 and 11-5)? So, Proceed: False.(b) Start: Defi ne exothermic. Information: Exothermic corresponds to a negative DH8(Section 2-1). Proceed: This statement is true.(c) Start: Read carefully! The problem says equally favorably, which means that, if thestatement is true, the hydrogenations of all alkenes will have exactly the same DH8. Information:Look at Figure 11-12. They dont. Proceed: False! So the only true statement is (b).