A) Number of moles of sodium carbonate after mixing the two
tanks can be calculated as below:
Total concentration of Na2CO3 = 3.00x10-2 M +
6.00x10-3 M
                                            Â
= 0.036M
Total volume of water is: (1.00x103 +
2.00x103) L
                                Â
= 3000L
in 1 mole of Na2CO3 ------------ 2 moles of Na+ ions are
there.
no. of moles = molarity * volume
                 Â
= 0.036M * 3000L
                 Â
= 108 moles of Na2CO3
Hence there will be 108* 2 = 216 moles of Na+ ions.
B) Concentration of sodium ions in the product:
Molarity = no.of moles/ volume in L
          Â
= 216 moles/ 3000 L
         Â
= 0.072M