Answer:I got pH = 4.98
Explanation:. This agrees with the fact that strong acid + weak base = acidic pH.
If you notice, the volume and concentration of both 
NH
3
 and 
HNO
3
 are identical, and 
HNO
3
 only has one 
H
+
. Therefore, you should convince yourself that these neutralize each other exactly because the number of mols of each are equal.
This leaves the same number of mols of 
NH
+
4
 as 
NH
3
, in TWICE the volume (i.e. don't forget to account for dilution!):