If in English you have an impersonal expression with two different subjects ("It is necessary that you do the dishes" or "It is necessary for you to do the dishes") always use in French que + a conjugated form of the subjunctive ("Il faut/est nécessaire que tu fasses la vaisselle").

    On the other hand, an impersonal expression can be used with an infinitive if there is only one grammatical subject. For instance: "It's necessary to wash your clothes on the weekend" ("Il faut faire la lessive le week-end").

    Notice that most impersonal expressions consist of être + an adjective and require de before a dependent infinitive. For instance: "Il est facile/fatiguant/dangereux/bon de conduire la nuit" ("It's easy/tiring/dangerous/good to drive at night").