a)MgCl2 +2NaOH --> Mg(OH)2 +2NaCl (*)
b) đổi :200ml=0,2(l)
=>nMgCl2=0,1(mol)
theo(*) :nMg(OH)2=nMgCl2=0,1(mol)
=>mMg(OH)2=5,8(g)
c)Mg(OH)2+2HCl--> MgCl2 +2H2O(1)
theo (1):nHCl=2nMg(OH)2=0,2(mol)
=>mHCl=7,3(g)
d)VHCl=\(\dfrac{0,2}{2}=0,1\left(mol\right)\)