Use the concentration and rate data presented in the table below to answer the f
ID: 787885 • Letter: U
Question
Use the concentration and rate data presented in the table below to answer the following questions about the hypothetic reaction:
A + 2B + 4C --> 2D + E
Line
A (Mol/L)
B (mol/L)
C (mol/L)
Rate (mol/L.s)
1
0.100
0.100
0.100
3.6 x 10-2
2
0.200
0.100
0.100
3.6 x 10-2
3
0.100
0.200
0.100
7.2 x 10-2
4
0.200
0.200
0.200
2.9 x 10-1
5
0.300
0.200
0.300
?
g) Propose a reaction mechanism using the criteria presented in the lesson, with the third step as a rate-determining step. 4 mks
h) Draw a potential energy diagram to illustrate this reaction mechanism, assuming that the overall reaction is endothermic. Label reaction intermediates with RI and activated complexes with AC. (3mks)
Line
A (Mol/L)
B (mol/L)
C (mol/L)
Rate (mol/L.s)
1
0.100
0.100
0.100
3.6 x 10-2
2
0.200
0.100
0.100
3.6 x 10-2
3
0.100
0.200
0.100
7.2 x 10-2
4
0.200
0.200
0.200
2.9 x 10-1
5
0.300
0.200
0.300
?
Explanation / Answer
second method:
The rate expression for this equation will be of the form
rate = A^a*B^b*C^c where A B C are concentrations
Compare lines two and four
A & B have same conc. C's conc. doubles
for this change in C's conc. , rate becomes 8 times ( 2.9/.36).
2^3 = 8
Order w.r.t. C = 3,c=3
Similarly compare 1 and 3, order w.r.t. B i.e. b = 1
Now, compare any two lines and putting in the values of A,B,C,b,c,rate in the rate law
find the value of a.,a = -1
The overall order = -1+1+3 = 3, Rate law : A^-1* B^1*C3
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