Answer:
Four.
Step-by-step explanation:
Hello!
In this case, according to the given chemical reaction:
Thus, since the reactants side (left) has three hydrogens in ammonia and one hydrogen in hydrochloric acid, we infer it has four hydrogen atoms at this side. Moreover, products side (right) has 4 hydrogen atoms as well, which means that the law of mass action is respected.
Best regards!