Since {HEAD ~ this reaction} is ArNH2+NO2 −+2H+→ArN2 ++2H2O, it theoretically requires two equivalents of {TAIL ~ an acid} 
Since { HEAD ~ this reaction } is ArNH2+NO2 −+2H+→ArN2 + +2H2O , it theoretically requires two equivalents of { TAIL ~ an acid }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL