where x is the molecular weight of Ammonium Hydroxide [NH4OH]
by solving, we get x = 8.75.
Now, moles of NH4OH is 8.75 / 35 = 0.25.
One mole of NH4OH is produced when One mole of NH3 reacts with One mole of H20
=> 0.25 moles of NH4OH is produced when 0.25 moles of NH3 reacts with x Moles of H20 [maybe 0.25].
Thus 0.25 moles of NH3 is 0.25 * 22.4 litres of NH3
=> 5.6 litres of NH3 is needed to prepare 100ml of 2.5M Ammonium Hydroxide Solution.