Question

The value of Kp for the reaction:

2NOBr <----> 2NO + Br₂
is 9.6 x 10^-3

What is the value for Kc for this reaction?

Answer 1

Kc = concentration of products / concentration of reactants

Kc = ([NO]²x[Br₂])/ [NOBr]²

Kp = Partial pressure of products / Partial pressure of reactants

Kc = ([P_NO]²x[P_Br2])/ [P_NOBr]²

The relation between Kc and Kp     Kp = Kc (RT)^∆n

R = gas constant = 0.08206 L.atm/K.mol

∆n = (Total moles of gas on the products side) - (Total moles of gas on the reactants side)

∆n = (2+1)-2 = 1

You did not provide temperature, so I am assuming this reaction was done at 27 °C

First we have to convert T in °C to kelvin

T (Kelvin) = T in °C+273 = 27 + 273 = 300 K

Kp = Kc (RT)^∆n   

Kp = 9.6 x 10^-3

Kc = Kp/(RT)^∆n   = (9.6 x 10^-3)/(0.0826x300)¹

Kc = 0.387 x 10^-3