To find the concentration of chloride #Cl^-# in the mixture we will first find the total number of mole of #Cl^-# (#n_("total")#) then divide it by the total volume (#V_("total")#) of the mixture.
#C_M=(n_("total"))/(V_("total"))#
To find the #n_("total")# we will calculate the number of mole coming from both salts:
#n_(LiCl)=C_MxxV=0.392(mol)/(cancel(L))xx2.50xx10^(-3)cancel(L)=9.80xx10^(-4)mol#
#n_(KCl)=C_MxxV=84.8xx10^(-3)(mol)/(cancel(L))xx34.5xx10^(-3)cancel(L)=29.3xx10^(-4)mol#
#n_("total")=n_(LiCl)+n_(KCl)=9.80xx10^(-4)mol+29.3xx10^(-4)mol=39.1xx10^(-4)mol#
The total volume is: #V_("total")=34.5 xx10^(-3)L+2.50xx10^(-3)L=37.0xx10^(-3)L#
The concentration can the be found by:
#C_M=(n_("total"))/(V_("total"))=(39.1xx10^(-4)mol)/(37.0xx10^(-3)L)=0.106M#
Therefore, the correct choice is (c) 106 mM.
