Learn Farsi: آیا به ترکیبات این سرم اعتماد می‌شود؟ - Are the ingredients of this serum trusted?

The active verb اعتماد کردن (to trust) always takes the preposition به (to). In this impersonal passive structure, the object (ترکیبات) keeps its preposition. So instead of 'Are the ingredients trusted?', Farsi literally says 'Is it trusted to the ingredients?'

Why is the verb می‌شود singular when ترکیبات (ingredients) is plural?

In an impersonal passive with a prepositional verb, the sentence has no grammatical subject. The phrase به ترکیبات acts as a prepositional object. Because there is no subject to agree with, the passive verb اعتماد می‌شود defaults to the third-person singular, regardless of whether the object is plural.

How do we form the impersonal passive for a compound verb like اعتماد کردن?

You keep the noun part of the compound (اعتماد) and change the active auxiliary کردن (to do) into the passive auxiliary شدن (to become), locking it in the third-person singular. Thus, اعتماد می‌کنند (they trust) becomes اعتماد می‌شود (it is trusted).

The word for ingredients is ترکیبات. Is this a regular Farsi plural?

No, ترکیبات uses the Arabic plural suffix ـات (-at). While native Farsi words usually take ـها or ـان, many formal or scientific nouns borrowed from Arabic, like ترکیب (compound/ingredient), take this suffix to form the plural.