2Fe + 6HCl -> 2FeCl3 + 3H2 If 7.0 moles of HCl is added to enough iron that the HCl is completely used up, how many moles of hydrogen gas will be produced?

3.5 moles of hydrogen gas will be produced.

Explanation:

The balanced chemical equation is:

As HCl gets completely used up, is the limiting reagent.

According to stoichiometry :

6 moles of produces =  3 moles of

Thus 7.0 moles of   produces=  of

 Thus 3.5 moles of hydrogen gas will be produced.

answer carbon and three oxygen atoms;