Which among the following is least acidic
The acidic strength of oxides decreases on moving down the group.Moreover, pentoxides are more acidic than trioxides. As the atomic no. of an element in 15 group increases, the acidic character decreases.
So, P4O10 > As4O6 and P4O10 > As4O10 . Due to increase in O.N. of an element acidic nature increases.Thus decreasing order of acidic strength is P4O10 > P4O6 > As4O10 > As4O6