7. b) C=md/ms*100 => md=C*ms/100=5,2*200/100=10,4g BaCl2
BaCl2 + H2SO4 = BaSO4 + 2HCl
MBaCl2= ABa+2ACl=137+2*35,5=208g/mol
MH2SO4=2AH+AS+4AO=2*1+32+4*16=98g/mol
208g BaCl2.....................98g H2SO4
10,4g BaCl2...................x=98*10,4/208= Calculeaza !!