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
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.