Question

Rate constants for the reaction
NO2(g)+CO(g)?NO(g)+CO2(g)
are 1.3M?1s?1 at 700 K and 23.0M?1s?1 at 800 K.

Part A

What is the value of the activation energy in kJ/mol?

Ea =

134

kJ/mol

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Correct

Part B

What is the rate constant at 770K ?

Express your answer using two significant figures.

k =

  /(M?s)

Answer 1

1)

Given:

T1 = 700 K

T2 = 800 K

K1 = 1.3 M-1.s-1

K2 = 23 M-1.s-1

use:

ln(K2/K1) = (Ea/R)*(1/T1 - 1/T2)

ln(23/1.3) = ( Ea/8.314)*(1/700 - 1/800)

2.8731 = (Ea/8.314)*(1.786*10^-4)

Ea = 133768 J/mol

Ea = 134 KJ/mol

Answer: 134 KJ/mol

2)

Given:

T1 = 700 K

T2 = 770 K

K1 = 1.3 M-1.s-1

Ea = 133768 J/mol

use:

ln(K2/K1) = (Ea/R)*(1/T1 - 1/T2)

ln(K2/1.3) = (133768.0/8.314)*(1/700 - 1/770.0)

ln(K2/1.3) = 16089*(1.299*10^-4)

ln(K2/1.3) = 2.09

(K2/1.3) = e^(2.09)

(K2/1.3) = 8.081

K2 = 10.51 M-1.s-1

Answer: 11 M-1.s-1