posted by rooftops .
What concentration of ammonia, [NH3], should be present in a solution with [NH4+]= 0.734M to produce a buffer solution with pH= 9.13? For NH3, Kb= 1.8x10^-5
Your posts have been removed because of your "homework dumping" -- a string of posts in quick succession with absolutely no sign that you have given any thought to anything.
Once you write up YOUR THOUGHTS, please re-post, and someone here will be happy to comment.
NH3 + H2O ==> NH4^+ + OH^
Kb = (NH4^+)(OH^-)/(NH3)
Convert pH to pOH, then to (OH^-), substitute into Kb. Also substitute into Kb what you want the (NH4^+) to be and solve for (NH3).