PLEASE HELP! DUE TODAY! How many gram of magnesium react with 120 ml H3PO4 (with molar concentration 2M)?

3.89 g Mg

Explanation:

2M = 2 mol/L

120 mL = 0.120 L

2 mol/L *0.120 L = 0.240 mol H3PO4

                               3Mg + 2H3PO4 > Mg3(PO4)2 + 3H2

from reaction         3 mol   2 mol

given                  0.240mol  x mol

x = 0.240*2/3 = 0.16 mol Mg

M(Mg) = 24.3 g/mol

24.3 g/mol *0.16 mol = 3.89 g Mg  

the correct answer is:

a. formation of precipitation