TBR Chem 3, Example 3.1

[MedPR]

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So the example question is "Which of the following graphs represents what is observed over time for a reaction starting with all reactants"

Since this is the chapter about equilibrium, I went ahead and assumed the question was referring to a reaction that ultimately reached equilibrium, though it wasn't stated that way.

One of the answer choices is obviously wrong.
One of the answer choices is obviously equilibrium
One of the answer choices shows a reaction that never reaches equilibrium, and always has a higher forward rate than reverse rate
One of the answer choices shows that the reaction equilibriates for an instant, then the rate of the reverse reaction overtakes the rate of the forward reaction.

If you didn't know this was a question from the equilibrium chapter, how would you be able to pick between answers 2, 3, and 4? (Answers A, B, and C for those of you with TBR Chem)

Page 166.

Edit: Not every reaction reaches equilibrium given enough time, correct?

 

[MT Headed]

Every reaction goes to equilibrium, given enough time.

Remember the arrhenius equation says that the rate of an elementary reaction in a particular direction depends on the concentration of the reactants for that direction. As you use up reactants (and make products, which would be the reactants for the reverse reaction) the rate forward slows, asymptotically, and the reverse rate grows to the same asymptote, until they are both equal.

None of the other answers make any sense.

 

[MedPR]

Every reaction goes to equilibrium, given enough time.

Remember the arrhenius equation says that the rate of an elementary reaction in a particular direction depends on the concentration of the reactants for that direction. As you use up reactants (and make products, which would be the reactants for the reverse reaction) the rate forward slows, asymptotically, and the reverse rate grows to the same asymptote, until they are both equal.

None of the other answers make any sense.

Thanks 🙂