Question

The following equilibrium pressures were observed at a certain temperature for the reaction.
N2(g) + 3 H2(g) <==> 2 NH3(g)
partial pressure of NH3 = 3.2 ✕ 10−1 atm
partial pressure of N2 = 1.6 ✕ 10−2 atm
partial pressure of H2 = 4.9 ✕ 10−2 atm
Calculate the value for the equilibrium constant Kp at this temperature.

i got 7.53e-4 by using
[NH3]^2/[N2][H2]^3
but it says my answer is wrong

Answer 1

Just examining it, your answer is wrong.

look at the denominator; 1.6E-2*(4E-2)^2 = 25.6E-6

that E-6 turns to E6 in the numerator, which fill force the power in the numerator to be high, nowhere near e-4
recalculate.

Answer 2

Thanks for showing what you did. I suspect you just punched in the wrong numbers because I don't get anything close to that.
If you estimate it as
(0.3)^2/(0.02)(0.05)^3
It is about 4E5.