To calculate the value of Kp, we need to use the relationship between Kp and Kc, which is:
Kp = Kc x (RT)^Δn
where R is the gas constant (0.082 L atm/mol K), T is the temperature in Kelvin, and Δn is the difference in the number of moles of gas on the product side and the reactant side (in this case, Δn = 2-3 = -1).
First, we need to convert the temperature from Celsius to Kelvin:
T = 227°C + 273.15 = 500.15 K
Next, we can plug in the values into the equation:
Kp = Kc x (RT)^Δn
Kp = 5.15 x (0.082 L atm/mol K x 500.15 K)^-1
Kp = 5.15 x (20.33 L/mol)^-1
Kp = 0.125 atm^-1
Therefore, the value of Kp at 227 degrees Celsius for the equilibrium 3A(g) ⇌ B(g) + D(g) with Kc=5.15 is 0.125 atm^-1.