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6. Thermodynamics and Kinetics

Enthalpy

6. Thermodynamics and Kinetics

Enthalpy

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How to calculate enthalpy using bond dissociation energies.

How to calculate enthalpy using bond dissociation energies.

Johnny Betancourt

Calculating Enthalpies

Calculating Enthalpies

Johnny Betancourt

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Multiple Choice
Predict the sign and magnitude of ∆H^oin kj/mol for the following reaction. Identify the reaction as either exothermic or endothermic.
Multiple Choice
If ΔH° is negative, what does this say about the favorability of a reaction?
Multiple Choice
Calculate ΔH° for the following reaction:
Textbook Question
Use bond-dissociation enthalpies [TABLE 4-2], p. 167) to calculate values of ΔH° for the following reactions.a. CH3—CH3 + I2 —> CH3CH2I + HI
Textbook Question
The bromination of methane proceeds through the following steps:1. Br2 + 2 Br• ΔH° (per mole)/+190 kJ (45 kcal)Ea (per mole)/ 190 kJ (45 kcal)2. CH4 + Br• —> CH3+ HBr +73 kJ (17 kcal) 79 kJ (19 kcal) 3. • CH3 + Br2 —> CH3Br + Br -112 kJ (-27 kcal) 4 kJ (1 kcal) d. Compute the overall value of ΔH° for the bromination
Textbook Question
Iodination of alkanes using iodine (I₂) is usually an unfavorable reaction. (See Problem 4-17 , for example.) Tetraiodomethane (CI₄) can be used as the iodine source for iodination in the presence of a free-radical initiator such as hydrogen peroxide. Propose a mechanism (involving mildly exothermic propagation steps) for the following proposed reaction. Calculate the value of ΔH for each of the steps in your proposed mechanism.
The following bond-dissociation energies maybe helpful:
Textbook Question
Use bond-dissociation enthalpies (Table 4-2, p. 167) to calculate values of ΔH° for the following reactions.
a. CH₃—CH₃ + I₂ → CH₃CH₂I + HI

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