Question

4 mol of NH3 on complete dissociation gives

Answer 1

Molarity of NH3=0.1mole/1Litre=0.1M
The raction can be given as :
NH3+H2O...........=NH4+....+OH-
0.1M.........................0.........10-7M (due to water)........initially
0.1M-x......................x....... .x+10-7 M..........at equilibrium
Here OH- comes from two sources :one from dissociation of water and the other source is the reaction of NH3 with water.
fom the question,x+10-7 M=10-3..M
so x=~10-3M

writting the dissociation constant, K=[NH4+][OH-]/[NH3]
K=x*x/0.1-x