nMg = 3.6/24 = 0.15 (mol)
nAgNO3 = 0.2*0.1 = 0.02 (mol)
Mg + 2AgNO3 => Mg(NO3)2 + 2Ag
0.01........0.02
=> nMg ( Pư với HBr) = 0.15 - 0.01 = 0.14 (mol)
Mg + 2HBr => MgBr2 + H2
0.14___0.28_________0.14
CM HBr = 0.28/0.3 = 0.93 (M)
VH2 = 0.14*22.4 = 3.136 (l)