Question

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

Answer 1

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)