one faraday  for  58.5 g

now find mass for 0.04F  

then find concentration of remaining solution  and find α from vant hoff factor  NaCl---->  NA+   +  Cl-

                                                                                                                                            1                  0             0

                                                                                                                                         1- α                   α            α 

now H+  conc = Cα            now find -log10 of it for ph

see the previous one solution submitted is half correct and the left part is not valid

u will ask why ,then the ans is that problem is with nacl so van't hoff factor will not be used

i have another method for it

ie  for 1F  1mole NaCl electrolysed thus for 0-04 F it will be 0.04 mole NaCl

number of nacl= no. of h2o dissociate , now h2 will be escaped out and in the solution we will left with 0.04 mole of OH- ion now  see for p(oH)  use conc of 1litre ,ie  0.04 in 400ml  for 1000ml =1litre find oH ion concentration and then pOH from that find pH=  14 - p(oH)

still i have doubt on this method too so it will better that u submit the correct pH value (ans) so that validity of this method can be checked and can serve our purpose , prompt action will be appreciated.