Question

Which of the following is not included in the net ionic equation for the reaction between $CaC{l_2}$ and $Na,{\text{ }}CO,$ to form calcium carbonate and sodium chloride?
A) $C{a^{2 + }}$
B) $CO_3^{2 - }$
C) $2N{a^ + }$
D) $CaC{O_3}$
E) All of the above

Answer 1

The net ionic equation is the equation in which only the actual reaction is represented, during a precipitation reaction. In such reactions two types of ions are found – spectator ion and reacting ions. Spectator ions do not participate in the reaction but stay as such while the reacting ions are the one participating in actual reaction.

Complete answer:
The overall reaction can be written as - $CaC{l_2}(aq) + N{a_2}C{O_3}(aq) \to CaC{O_3}(s) + 2NaCl(aq)$
Since, $N{a^ + }\& C{l^ - }$ ions are the ions which are in ionised form before and after the reaction and remain unchanged by the reaction, thus they play the role of spectator ions. They remain unchanged in the solution. The other two ions present in the solution which are reacting actually are - $C{a^{2 + }}\& CO_3^{2 - }$ , both these ions react to form calcium carbonate as –
$C{a^{2 + }}(aq) + CO_3^{2 - }(aq) \to CaC{O_3}(s)$
This indicates the net ionic reaction, hence there are only three species in the net ionic equation, i.e.
$C{a^{2 + }},CaC{O_3}\& CO_3^{2 - }$
Thus, the ion which is not included in the net ionic equation for the reaction between $CaC{l_2}$ and $Na,{\text{ }}CO,$ to form calcium carbonate and sodium chloride is $N{a^ + }$.

Hence, the correct option is C) $2N{a^ + }$ .

Note:
In a net ionic equation, the spectator ions are not represented because they do not take part in the reaction. Only the ions, that react with one another and the form precipitate, are represented in a net ionic equation.