I'm really struggling how to explain this problem regarding colligative properties in my thermodynamics course. I've attached a picture, and would appreciate help!

We have a system consisting of water and a salt. The standard state we choose is pure water and pure salt at infinite dilution, at 1 bar and 273K, so that GH2Oo(273K)=GH2Oliq(1bar,273K)0GSo(273K)=Gsaq(1bar,273K)0 where we use lowered s for salt. Furthermore, we will deal with the famous salt Mv+Xv which dissolves after the reaction Mv+Xvv+Mz++vXz Table 1: Values for water at 1 bar and 273K, for the standard state chosen in this problem. Assume that the enthalpy of mixing for the salt solution is ideal, and explain that the molar entropy of the salt solution then is given by Smsol=xH2OSm,H2Oo+xsSm,soR(xH2OlnxH2O+x+lnx++xlnx) Where x+and xare the mole fractions of positive and negative ions. When is xH2OlnxH2O=0 a good approximation? When is x+=v+xs and x=vxs good approximations? When is xH2OGm,H2Oo+xsGm,SoGm,H2Oo a good approximation