Kerala KEAM 5 June 2024 Solved Paper

In the carbonate ion ($CO_3^{2-}$), we can calculate the sum of the oxidation numbers as follows:- The oxidation number of oxygen in the carbonate ion is $-2$, as oxygen generally has an oxidation state of $-2$ in compounds.- Let the oxidation number of carbon be $x$.- Since the overall charge on the carbonate ion is $-2$, we can set up the following equation for the sum of oxidation numbers:$$x + 3(-2) = -2.$$Simplifying this equation: $$x - 6 = -2 \quad \Rightarrow \quad x = +4.$$Thus, the oxidation number of carbon is $+4$, and the oxidation numbers of the three oxygen atoms are each $-2$.Now, summing these oxidation numbers: $$+4 + 3(-2) = +4 - 6 = -2.$$Therefore, the sum of the oxidation numbers of all the atoms in the carbonate ion is $-2$.Thus, the correct answer is $-2$, which corresponds to option (C). Quick Tip: In polyatomic ions like carbonate, remember that the sum of the oxidation numbers of all atoms equals the charge on the ion. The oxidation number of oxygen is typically $-2$, and the overall charge determines the oxidation number of other elements.