J.R. S. answered • 01/15/19

Ph.D. University Professor with 10+ years Tutoring Experience

1. Write the balanced eq:

Mg + 2HCl ==> MgCl_{2} + H_{2}

moles H_{2 }formed: PV = nRT. P = pressure AFTER subtracting vapor pressure of water at 20 degrees from 725 mm. Tge v.p. Of water can be found in a text book or reference table. Solve for n=PV/RT

Next, moles Mg = moles H_{2} based on stoichiometry of the equation.

Finally, mass Mg = moles Mg x atomic mass Mg

2. Same approach as in #1. Find moles of H_{2} after subtracting vapor pressure of water and solving for n in n = PV/RT. Then, moles Mg consumed = moles H_{2} formed. Mass of Mg consumed = moles Mg x atomic mass of Mg