What is the pOH of a 0.2M buffer solution of NH 4 + 0.2M NH4NO3 at 25 ° C.

PKP = 4.74

Actually you need to repost the question. Did you make a typo? Is that NH3? And when one normally talks about a 0.2M buffer one means the TOTAL is 0.2 but you have 0.2 for each of two materials. I assume that is 0.2M NH3 and 0.2M NH4NO3.