2M of 100 ml Na2SO4  is mixed with 3M of 100 ml  NaCl   solution and 1M of  200 ml CaCl2 solution. Then the ratio of the concentration of cation and anion is ___?

Solution: Number of moles =  Molarity × volume of solution in litre         Number of moles of Na2SO4=2×0.1=0.2        Number of moles of NaCl=3×0.1=0.3        Number of moles of CaCl2=1×0.2=0.2        Number of moles of cation (0.2×2)+0.3+0.2=0.9        Number of moles of anion 0.2+0.3+(0.2×2)=0.9          Ratio of number of moles of cation to anion is=0.9 / 0.9=1