The reaction `CaCO_(3)(s) hArr CaO(s)+CO_(2)(g)` reaches the state of equilibrium when

Options

A. Partial pressure of `CaCO_(3)` become constant
B. Partial pressure of CaO become constant
C. Pressure of `CO_(2)` become constant
D. All partial pressure keep changing

Answer

To solve the question regarding the equilibrium state of the reaction \( \text{CaCO}_3(s) \rightleftharpoons \text{CaO}(s) + \text{CO}_2(g) \), we can follow these steps:

### Step 1: Identify the components of the reaction
The reaction involves:
- Reactant: Calcium carbonate (\( \text{CaCO}_3 \)) in solid form.
- Products: Calcium oxide (\( \text{CaO} \)) in solid form and carbon dioxide (\( \text{CO}_2 \)) in gaseous form.

### Step 2: Understand the concept of equilibrium
Chemical equilibrium is reached when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products over time.

### Step 3: Analyze the reaction components
In this reaction, both \( \text{CaCO}_3 \) and \( \text{CaO} \) are solids. In equilibrium expressions, the concentrations of solids do not appear because they are constant. Therefore, the equilibrium expression will only involve the gaseous component.

### Step 4: Write the equilibrium expression
For the reaction, the equilibrium constant \( K_p \) can be expressed as:
\[ K_p = \frac{P_{\text{CO}_2}}{1} = P_{\text{CO}_2} \]
where \( P_{\text{CO}_2} \) is the partial pressure of carbon dioxide.

### Step 5: Determine the condition for equilibrium
The reaction reaches equilibrium when the partial pressure of \( \text{CO}_2 \) becomes constant. This means that the amount of \( \text{CO}_2 \) produced from the decomposition of \( \text{CaCO}_3 \) will no longer change, indicating that the system has reached a state of balance.

### Conclusion
Thus, the reaction \( \text{CaCO}_3(s) \rightleftharpoons \text{CaO}(s) + \text{CO}_2(g) \) reaches the state of equilibrium when the partial pressure of \( \text{CO}_2 \) becomes constant.

### Final Answer
The equilibrium is reached when the partial pressure of \( \text{CO}_2 \) becomes constant.

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