Is the congregational dua Sunnah?

Answer

We presume that you are referring to the Dua after Fardh Salaat. It is Sunnah to raise the hands and make Dua after every Fardh Salaat. However, while ostensibly it appears to be a congregational dua, in reality it is an individual dua. It is not obligatory for the musallis to begin and end the dua with the Imaam. The dua should be made silently, and every one should make his own dua. The loud dua which is made in congregation is bid'ah.