`CO_2` is an acidic oxide and reacts with bases forming two series of salts bicarbonates and carbonates `CO_2` dissolves in water also, slightly, to form `H_2CO_3`
When `CO_2` dissolves in water, the ions that are present in equilibrium are

Options

A. `CO_3^(2-)`
B. `HCO_3^(-)`
C. `H_3O^+`
D. All of these

Answer

To determine the ions present in equilibrium when \( CO_2 \) dissolves in water, we can follow these steps:

### Step 1: Understand the Reaction
When carbon dioxide (\( CO_2 \)) dissolves in water, it reacts to form carbonic acid (\( H_2CO_3 \)). The reaction can be represented as:
\[ CO_2 (g) + H_2O (l) \rightleftharpoons H_2CO_3 (aq) \]

### Step 2: Dissociation of Carbonic Acid
Carbonic acid is a weak acid and can dissociate in water to form bicarbonate (\( HCO_3^- \)) and hydrogen ions (\( H^+ \)). This can be represented as:
\[ H_2CO_3 (aq) \rightleftharpoons HCO_3^- (aq) + H^+ (aq) \]

### Step 3: Establish the Equilibrium
The equilibrium established in the solution includes the following species:
- Carbonic acid (\( H_2CO_3 \))
- Bicarbonate ion (\( HCO_3^- \))
- Hydrogen ion (\( H^+ \))

### Step 4: Identify the Ions Present
From the above dissociation, we can conclude that the ions present in equilibrium when \( CO_2 \) dissolves in water are:
- \( H^+ \) (hydrogen ion)
- \( HCO_3^- \) (bicarbonate ion)

### Final Answer
The ions present in equilibrium when \( CO_2 \) dissolves in water are \( H^+ \) and \( HCO_3^- \).

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