Reaction is NH4OH <-> NH4+ OH- (note this is reversible)
Draw up an ICE table
Let x be equilibrium conc of OH- assume init conc of OH is 0M and init conc of NH4+ is 0M also. Init conc of NH4OH is 0.1M so equilibrium conc will be 0.1-x.
%dissociation = x/0.1-x * 100%
1 = 100x/0.1-x
0.1-x = 100x
101x = 0.1
x = 0.0009901
pOH = -log(0.0009901) = 3.00
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