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Consider the reaction A+2BC whose rate at 25 C was measured using three differen

ID: 877569 • Letter: C

Question

Consider the reaction

A+2BC

whose rate at 25 C was measured using three different sets of initial concentrations as listed in the following table:

7.7×103

What is the rate law for this reaction?

Express the rate law symbolically in terms of k, [A], and [B].

Part A

where R is the gas constant (8.314 J/molK)

The activation energy of a certain reaction is 38.2 kJ/mol . At 26  C , the rate constant is 0.0120s1. At what temperature in degrees Celsius would this reaction go twice as fast?

Express your answer with the appropriate units.

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Part B

Given that the initial rate constant is 0.0120s1 at an initial temperature of 26  C , what would the rate constant be at a temperature of 200  C for the same reaction described in Part A?

Express your answer with the appropriate units.

Trial [A]
(M) [B]
(M) Rate
(M/s) 1 0.40 0.010 1.9×103 2 0.40 0.020 3.8×103 3 0.80 0.010

7.7×103

Explanation / Answer

1)

A + 2B   <-------------------> C

rate= k [A]x [B]y

1.9 x 10^-3 = k [0.4]x [0.010]y -----------------> (1)

3.8 x 10^-3 = k [0.4]x [0.020]y ------------------> (2)

7.7 x 10^-3 = k [0.8]x [0.010]y ------------------> (3)

if we solve 1 diveded by 2 we get y = 1, if we solve 3 diveded by 1 we get x = 2

x = 2 , y = 1

rate = k [A] 2 [B] 1

rate = k [A] 2 [B] 1

1.9 x 10^-3 = k [0.4] 2 [0.010] 1

k = 1.187 L2 mol2 s1

PART A :

log(k2/k1) = ( Ea/2.303R)[1/T1-1/T2]

log (2k1/k1) = (38.2 / 2.303 x 8.314 x 10^-3) [1/299-1/T2]

T2 = 313 K

T2 = 400C

PART B :

T1 = 26 + 273 = 299 K

T2 = 200 + 273 = 473 K

k1 = 0.0120 s^-1

log(k2/k1) = ( Ea/2.303R)[1/T1-1/T2]

log (k2/ 0.0120) = (38.2 / 2.303 x 8.314 x 10^-3) [1/299-1/473]

log (k2/ 0.0120) = 2.45

(k2/ 0.0120) = 281.83

k2 = 3.382 s-1

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