Question

what is the concentration of na and co3 ions in 0.2M aqueous solution of na2co3

Answer 1

You really need to find the caps key and use it. CO, Co, co all mean something different.

Na2CO3 ==> 2Na^+ + CO^3-
0.2M Na2CO3 gives 0.2M x 2 = 0.4 for (Na^+) and 0.2 x 1 = 0.2M for (CO3)2-