a) Mg+2HCl--->MgCl2+H2
n H2=3,36/22,4=0,15(mol)
n HCl=2n H2=0,3(mol)
m HCl=0,3.36,5=10,95(g)
C% HCl=10,95/73.100%=15%
b)2 R+2xHCl-->2RClx+xH2(2)
n HCl(2)=2,5n HCl(1)=0.75(mol)
m HCl=0,75.36,5=27,375(g)
n H2=1/2n HCl=0,375(mol)
m H2=0,75(g)
m R=m H2+m Muôi-m HCl=0,75+51-27,375=24,375(g)
n R=1/x n HCl=0,75/x(mol)
M R=24,375 : 0,75/x=32,5x
+x=2--->R=65(Zn)
Vậy R là Zn