Mathematical Relationships of Temperature, k, and Rate, including the Calculate
ID: 979476 • Letter: M
Question
Mathematical Relationships of Temperature, k, and Rate, including the Calculate the E_a Identify the rate law you reported in Part 1. Use Experiment Trial 2 results again (From Part II of the Lab) Record your rate law from Part 1B question C here. Calculate the rate constant, k, at 25 degree C and at 45 degree C - include the correct units for k. [Recall Rate units = (M/s).] k at 25 degree C = (You calculated this in Part 1B at Question D. k at 45 degree C = Given the temp change (25 degree C to 45 degree C) and the k values calculated above, calculate the E_a of this reaction. See equation 16.10 in your book. Show your work! , ln k_2/k_1 = E_a/R (1/T_1 - 1/T_2) Assume the reaction you measured contains a catalyst, would you expect the reaction to have a higher or lower E_a, if the catalyst is removed, given any constant temperature?Explanation / Answer
A)
at 25 oC :
compare trial 1 and 2:
when concentration of I- gets halfed and that of S2O82- is same, rate become half
So order with respect to I- = 1
compare trial 1 and 3:
when concentration of S2O82- gets halfed and that of I- is same, rate become half
So order with respect to S2O82- = 1
Rate = K [S2O82-] [I-]
at 45 oC :
compare trial 1 and 2:
when concentration of I- gets halfed and that of S2O82- is same, rate become half
So order with respect to I- = 1
compare trial 1 and 3:
when concentration of S2O82- gets halfed and that of I- is same, rate become half
So order with respect to S2O82- = 1
Rate = K [S2O82-] [I-]
B)
at 25 oC:
Rate = K [S2O82-] [I-]
put values from trial 1:
2.78*10^-5 = K*0.03*0.12
K =7.72*10^-3 M-1s-1
at 45 oC:
Rate = K [S2O82-] [I-]
put values from trial 1:
1.67*10^-4 = K*0.03*0.12
K =4.64*10^-2 M-1s-1
C)
T1 = 25 oC = (25+273) k = 298 K
T2 = 45 oC = (273 + 45) = 318 K
ln(K2/K1) = Ea/R * (1/T1 - 1/T2)
ln (4.64*10^-2 / 7.72*10^-3) = Ea / 8.314 * (1/298 - 1/318)
1.79 = Ea / 8.314 * (2.11*10^-4)
Ea = 70531 J/mol
= 70.5 KJ/mol
D)
If catalyst is removed Ea will increase. This is how catalyst works