Question

Using the given data, calculate the rate constant of this reaction. A+B yield C+D

A [M] B [M] rate

.370, .340 .0210

.370 .782 .111

.592 .340 .0336

STRATEGY: 1. Determine the rate law. 2. Solve the rate law for k and calculate the k value.

Answer 1

Rate = k*[A]^a[B]^b

then

Rate1 = k*[A1]^a[B1]^b

Rate2 = k*[A2]^a[B2]^b

divide 1 and 2

Rate1/Rate2 = k*[A1]^a[B1]^b / k*[A2]^a[B2]^b

then

Rate1/Rate2 = ([[A1]([A2]^a) * ([B1]/[B2]^b)

substitute 1 and 2

Rate1/Rate2 = ([[A1]([A2]^a) * ([B1]/[B2]^b)

0.021/0.111= ([[0.37]([0.37]^a) * ([0.34]/[0.782]^b)

0.18918918918 = 0.4347^b

b = ln(0.18918918918 )/(ln(0.4347)) = 1.99857

then b = 2 or 2nd order

for a

use point 1 and 3

Rate1/Rate3 = ([[A1]([A3]^a) * ([B1]/[B3]^b)

0.021/0.0336= ([[0.37/0.592^a)

0.625 = 0.625^a

a = 1

then

Rate = K*[A][B]^2

for K

just substitute any value, I will take 1st point

K = RATE/([A][B]^2) = 0.021/(0.37*0.34^2) = 0.49097540447

K = 0.49097540447