Question

The gas-phase reaction of NO with F2 to form NOF and F has an activation energy of Ea = 6.30 kJ/mol and a frequency factor of A = 6.00×10⁸M−1⋅s−1 . The reaction is believed to be bimolecular:

NO(g)+F2(g)→NOF(g)+F(g)

What is the rate constant at 695 ∘C ?

Express your answer to three significant digits with the appropriate units. For compound units, place a multiplication dot between units (e.g. J⋅mol−1⋅K−1).

(I got 2.74*10^8 M-1s-1 but it is wrong. I got a message saying "Enter your answer using dimensions of rate constant units for second-order reaction". Can someone please help me?)

Answer 1

Arrhenius equation can be written as:

K =Ae^{-(E_A / RT)}

write all the data in SI units to avoid any confusion

A = 6.00×108 M⁻¹⋅s⁻¹

Ea = 6.30 kJ/mol = 6300 J/mol

R = 8.314 J/mol.K

T = 695 ⁰C = 695+273 = 978K

putting in equation we get:

K =Ae^{-(E_A / RT)}

  = 6.00×10⁸ M⁻¹⋅s⁻¹e^{-(6300 J/mol/ 8.314 J/mol.K .978K)}

=2.76 x 10⁸ M⁻¹⋅s⁻¹ or

= 2.76 x 10⁸ L^-1.mol⁺¹.s^-1

your answer seems correct

and the dimension of rate constant (K) is same as frequency factor (A)