6,50g of ZnSO4 is 0,04 moles
Mass of ZnSO4 :
m=6,50g
Molar mass of ZnSO4 :
M=M(Zn)+M(S)+4*M(O)
M=65,38 g/mol+32,06 g/mol+4*15,99 g/mol
M=161,40 g/mol
Molarity of ZnSO4 :
n=m/M
n=6,50g/161,40g/mol
n=0,04 mol