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Ch.14 - Chemical Kinetics

Chapter 14, Problem 101a

This reaction has an activation energy of zero in the gas phase: CH3 + CH3 → C2H6 a. Would you expect the rate of this reaction to change very much with temperature?

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hey everyone in this example, we need to identify the relationship between the reaction rate and temperature. So we want to recall our formula where our rate constant K. Is equal to our frequency factor represented by a here, which is then multiplied by Euler number which is raised to our activation energy divided by r gas constant times the temperature. We can also interpret this equation by saying that we can take the L. N. Of the rate constant for a single reaction At different absolute temperatures. So we would therefore have to rate constants K. one And then that is going to be placed over K two. So just to be clear, these are the rate constants for a single reaction at two absolute, We can say two different absolute temperatures and now we can set this equal to our activation energy divided by r gas constant. R. Where now we're going to multiply by the inverse values of our initial temperature. T one Subtracted from the inverse value of our final temperature T. two. And so here it's clear that our rate constant K. Is directly related to temperature. And so we can say that therefore if we increase our rate constant or we can say if we increase our temperature, we would also increase our rate constant. So the answer here is that they have a direct relationship. So this would be our final answer. To complete this example. If you have any questions please leave them down below and I will see everyone in the next practice video
Related Practice
Textbook Question

The kinetics of this reaction were studied as a function of temperature. (The reaction is first order in each reactant and second order overall.)

C2H5Br(aq) + OH- (aq) → C2H5OH(l) + Br- (aq)

Temperature (°C) k (L,mol •s)

25 8.81⨉10-5

35 0.000285

45 0.000854

55 0.00239

65 0.00633

c. If a reaction mixture is 0.155 M in C2H5Brand 0.250 M in OH-, what is the initial rate of the reaction at 75 °C?

Textbook Question

The reaction 2 N2O5 → 2 N2O4 + O2 takes place at around room temperature in solvents such as CCl4. The rate constant at 293 K is found to be 2.35⨉10-4 s-1, and at 303 K the rate constant is found to be 9.15⨉10-4 s-1. Calculate the frequency factor for the reaction.

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Open Question
a. This reaction has an activation energy of zero in the gas phase: CH3 + CH3 → C2H6. b. Why might the activation energy be zero? c. What other types of reactions would you expect to have little or no activation energy?
Textbook Question

Consider the two reactions:

O + N2 → NO + N Ea = 315 kJ/mol

Cl + H2 → HCl + H Ea = 23 kJ/mol

a. Why is the activation barrier for the first reaction so much higher than that for the second?

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Textbook Question

Consider the two reactions:

O + N2 → NO + N Ea = 315 kJ/mol

Cl + H2 → HCl + H Ea = 23 kJ/mol

b. The frequency factors for these two reactions are very close to each other in value. Assuming that they are the same, calculate the ratio of the reaction rate constants for these two reactions at 25 °C.

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Textbook Question

Anthropologists can estimate the age of a bone or other sample of organic matter by its carbon-14 content. The carbon-14 in a living organism is constant until the organism dies, after which carbon- 14 decays with first-order kinetics and a half-life of 5730 years. Suppose a bone from an ancient human contains 19.5% of the C-14 found in living organisms. How old is the bone?

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