In the chemical reaction, mg + 2hcl mgcl2 + h2 how many moles of hcl are needed to completely react with 3.5 moles of mg? a. 3.0 b. 2.0 c. 7.0 d. 3.5 reset submit

Chemical Reaction:   Mg    +  2 HCl   →  MgCl₂  +  H₂

The mole ratio (ratio of numbers used to balance the two specimens in the equation) of Mg : HCl is 1 : 2

Thus there are twice as many moles of HCl in the reaction as there is Mg.

Since the mole of Mg =  3.5 mol

then the mole of HCl = 7 mol
     
    ∴ the answer is 7 mol (Option C)