Identify the common ions from the following compounds and write the balance chemical equations to show how its compound has formed.

Here are the common ions and their formation equations:

a) $\text{NO}_3^-$

• Common ion: Nitrate ion ($\text{NO}_3^-$)
• Formation of its compound (e.g., sodium nitrate):

$$\text{NaOH}(\text{aq}) + \text{HNO}_3(\text{aq}) \rightarrow \text{NaNO}_3(\text{aq}) + \text{H}_2\text{O}(\text{l})$$

b) $\text{H}_3\text{O}^+$

• Common ion: Hydronium ion ($\text{H}_3\text{O}^+$)
• Formation of its compound (e.g., in an acidic solution):

$$\text{HCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) \rightarrow \text{H}_3\text{O}^+(\text{aq}) + \text{Cl}^-(\text{aq})$$

c) $\text{S}(\text{CH}_3)_3$

• Common ion: Trimethylsulfonium ion ($\text{S}(\text{CH}_3)_3^+$)
• Formation of its compound (e.g., trimethylsulfonium iodide):

$$\text{CH}_3\text{SCH}_3(\text{l}) + \text{CH}_3\text{I}(\text{l}) \rightarrow (\text{CH}_3)_3\text{S}^+\text{I}^-(\text{s})$$

d) $\text{H}_2\text{CO}_2$

• Common ion: Formate ion ($\text{HCOO}^-$) (derived from formic acid, $\text{HCOOH}$)
• Formation of its compound (formic acid):

$$\text{CO}(\text{g}) + \text{H}_2\text{O}(\text{l}) \rightleftharpoons \text{HCOOH}(\text{aq})$$

e) $\text{H}_3\text{COH}$

• Common ion: Methoxide ion ($\text{CH}_3\text{O}^-$) (derived from methanol, $\text{CH}_3\text{OH}$)
• Formation of its compound (methanol):

$$\text{CO}(\text{g}) + 2\text{H}_2(\text{g}) \xrightarrow{\text{catalyst}} \text{CH}_3\text{OH}(\text{g})$$

f) $\text{NH}_4^+$

• Common ion: Ammonium ion ($\text{NH}_4^+$)
• Formation of its compound (e.g., ammonium chloride):

$$\text{NH}_3(\text{g}) + \text{HCl}(\text{g}) \rightarrow \text{NH}_4\text{Cl}(\text{s})$$