`CaCO_(3) hArr CaO + CO_(2)` reaction in a lime kiln goes to completion because

Options

A. It is a heterogeneous reaction
B. Backward reaction is very slow
C. `CO_(2)` formed escapes out
D. `K_(C)` (or) `K_(p)` has no unit

Answer

To explain why the reaction \( \text{CaCO}_3 \rightleftharpoons \text{CaO} + \text{CO}_2 \) goes to completion in a lime kiln, we can break down the reasoning step by step:

### Step 1: Understanding the Reaction
The reaction involves the decomposition of calcium carbonate (\( \text{CaCO}_3 \)) into calcium oxide (\( \text{CaO} \)) and carbon dioxide (\( \text{CO}_2 \)). This is a heterogeneous reaction because it involves different phases (solid \( \text{CaCO}_3 \) and gaseous \( \text{CO}_2 \)).

**Hint:** Identify the phases of the reactants and products in the reaction to understand its nature.

### Step 2: Conditions in a Lime Kiln
In a lime kiln, the reaction occurs in an open system. This means that the products of the reaction, particularly the gaseous \( \text{CO}_2 \), can escape freely into the atmosphere.

**Hint:** Consider how the physical setup of the reaction (open vs. closed system) affects the behavior of the products.

### Step 3: Le Chatelier's Principle
According to Le Chatelier's Principle, if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system will adjust to counteract that change. In this case, the removal of \( \text{CO}_2 \) gas from the system reduces the concentration of the product.

**Hint:** Recall Le Chatelier's Principle and how it applies to changes in concentration of reactants or products.

### Step 4: Effect of Escaping \( \text{CO}_2 \)
As \( \text{CO}_2 \) escapes from the kiln, the concentration of the product decreases. This shift in concentration causes the equilibrium to shift towards the right (forward direction) to produce more \( \text{CO}_2 \) and \( \text{CaO} \).

**Hint:** Think about how the removal of a product influences the direction of the equilibrium shift.

### Step 5: Completion of Reaction
Since the reaction continuously shifts to the right to replace the \( \text{CO}_2 \) that escapes, the reaction effectively goes to completion. The backward reaction (formation of \( \text{CaCO}_3 \) from \( \text{CaO} \) and \( \text{CO}_2 \)) is very slow under these conditions, further ensuring that the forward reaction dominates.

**Hint:** Analyze the speed of the forward and backward reactions and how they contribute to the completion of the reaction.

### Conclusion
Thus, the reaction \( \text{CaCO}_3 \rightleftharpoons \text{CaO} + \text{CO}_2 \) goes to completion in a lime kiln due to the continuous removal of \( \text{CO}_2 \), which shifts the equilibrium towards the products.