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CHMA11H3 Lecture 5: CHMA11H3 Lecture 5 Chapter 13

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fuchsiabee599
20 Sep 2018
School
UTSC
Department
Chemistry
Course
CHMA11H3
Professor
ALL

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CHMA11H3 Full Course Notes
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Document Summary

The equation above can relate the two rate constants at two different temperatures. Solution: assign the given values: (cid:1837)(cid:2869)=(cid:884). (cid:887)(cid:889) (cid:1838)(cid:1865)(cid:1867)(cid:1864) (cid:1871);(cid:2869)=(cid:889)(cid:882)(cid:883) (cid:1837);(cid:1837)(cid:2870)=(cid:887)(cid:888)(cid:889) (cid:1838)(cid:1865)(cid:1867)(cid:1864) (cid:1871);(cid:2870)=(cid:890)(cid:891)(cid:887) (cid:1837) Then, substitute the values to the equation given above. ln((cid:1837)(cid:2870)(cid:1837)(cid:2869))=(cid:1831)(cid:3028)((cid:883)(cid:2869) (cid:883)(cid:2870)) ln(cid:4684)(cid:887)(cid:888)(cid:889) (cid:1838)(cid:1865)(cid:1867)(cid:1864) (cid:1871) (cid:884). (cid:887)(cid:889) (cid:1838)(cid:1865)(cid:1867)(cid:1864) (cid:1871)(cid:4685)=(cid:1831)(cid:3028)( (cid:883)(cid:889)(cid:882)(cid:883) (cid:1837) (cid:883)(cid:890)(cid:891)(cid:887) (cid:1837)) Increasing the temperature raises the kinetic energy of the reactant molecules: there is a minimum amount of kinetic energy needed for the collision to be converted into enough potential energy to form the activated complex. Increasing the temperature increases the number of molecules with sufficient kinetic energy to overcome the activation energy: bond needs energy to break or to form bonds. Maximum rate: the rate of collisions with enough energy. Activation energy: the amount of energy needed to convert reactants into the activated complex. It is a chemical species with partially broken and partially formed bonds. This is always high in energy because of its partial bonds.

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Related Questions

2 things:

1. How did they flip 5.40=Ea/R(3.09x10^-4/K) to Ea=5.40 (K/3.09X10^-4)R

2: SOLVE 14.8!!!!

You are part of a team working on the development of a process in which a mineral species (labeled A for proprietary reasons) undergoes a reaction to form a new pigment to be used in house paints. In a series of experiments in a large well-mixed stirred tank reactor, you fill a tank with a known quantity of an inert liquid, bring the liquid up to a specified temperature, add a known quantity of A, and measure the concentration of A in the tank as a function of time. The reaction gives off heat as it progresses, but cooling water circulating in a jacket around the reactor keeps the temperature of the reacting mixture constant. The following data are recorded.

Concentration of A, CA(mol A/L)

t(min)

T = 94°C

T = 110°C

T = 127°C

T = 142°C

10

9.30×10−2

5.19×10−2

2.10×10−2

9.87×10−3

20

6.17×10−2

2.35×10−2

1.33×10−2

5.55×10−3

30

4.41×10−2

1.91×10−2

8.15×10−3

3.97×10−3

40

3.12×10−2

1.45×10−2

5.92×10−3

2.45×10−3

50

2.58×10−2

1.01×10−2

4.48×10−3

2.27×10−3

60

9.30×10−2

9.50×10−3

4.36×10−3

1.83×10−3

A research article indicates that concentration of A should vary with time according to the following expression:

CA(t)=11CA0+kt

(1)

where CA0 (mol/L) is the initial concentration of A in the reactor [CA(t=0)] and k is called the reaction rate constant. Despite being called a constant, k is a strong function of the absolute temperature in the reactor:

k(T)=k0 exp−EaRT(K)

(2)

In this equation (known as the Arrhenius equation after the Swedish chemist who proposed it), k0 is a constant, Ea(J/mol) is the reaction activation energy, and R=8.314 J/(mol·K) is the universal gas constant. Your task will be to verify that the expressions for CA(t) and k(T) fit the data, and if they do, to determine the parameters CA0 and k at each temperature and then the constants k0 and Ea.

(a)

What are the units of k, k0, and Ea if CA is in mol/L and t is in min?

(b)

Transform Equation 1 into an equation of the form y=at+b, so that if Equation 1 is valid, a plot of yvs. t would be a straight line. How would you determine CA0 and k from the slope and intercept of the line?

(c)

Create an Excel spreadsheet with the structure shown as Rows 1-10 in the figure at the end of this problem statement, and fill in the data table in Columns A-I. Then create the four scatterplots shown in Rows 15-21. In the “Trendline” options of each plot, check the boxes for “Display equation on chart” and “Display R-squared value on chart” but not the one for “Set intercept.” R2 is the coefficient of determination (it has several other names as well), and provides a measure of how well a straight line fits a set of data: the closer it is to 1, the better the fit. What can you conclude about Equation 1 from the four plots?

(d)

From the four trendline equations, calculate the values of k and CA0 for each of the four experimental temperatures and fill in Columns B-I in Rows 12 and 13 of the spreadsheet.

(e)

Enough A was initially added to the tank to make the initial concentration CA0=0.25 mol/L, yet you calculated four different values of CA0 in Part d. How do you explain this result?