Two flasks A and B of equal volume containing `NH_(3)` and HCl gases, are connected by a narrow tube of negligible volume. The two gases were prevented from mixing by stopper fitted in connecting tube. For further details of the experiment, refer to the given figure. What will be final pressure (in mm of Hf) in each flask when passage connecting two tubes are opened, assuming ideal gas behaviour of `NH_(3) and HCl` gas and the reaction
`NH_(3)(g)+HCl(g)rarrNH_(4)Cl(s)` goes to completion.

Answer

40