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For the reactions, (i) H(2)(g)+Cl(2)(g...

For the reactions,
(i) `H_(2)(g)+Cl_(2)(g)rarr 2HCl(g)+ xKJ`
(ii) `H_(2)(g)+Cl_(2)(g)rarr 2HCl(l)+ yKJ`
Which one of the following statement is correct :

A

x gt y

B

x lt y

C

x = y

D

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The correct Answer is:
To solve the problem, we need to analyze the two reactions given and determine the relationship between the enthalpy changes (X and Y) for the reactions. ### Step-by-Step Solution: 1. **Identify the Reactions**: - Reaction (i): \( H_2(g) + Cl_2(g) \rightarrow 2HCl(g) + x \, \text{kJ} \) - Reaction (ii): \( H_2(g) + Cl_2(g) \rightarrow 2HCl(l) + y \, \text{kJ} \) 2. **Understand the Nature of the Reactions**: - In reaction (i), hydrogen and chlorine gases react to form gaseous hydrogen chloride (HCl) and release \( x \, \text{kJ} \) of energy. - In reaction (ii), the same reactants form liquid hydrogen chloride (HCl) and release \( y \, \text{kJ} \) of energy. 3. **Reverse Reaction (ii)**: - If we reverse reaction (ii), we get: \[ 2HCl(l) \rightarrow H_2(g) + Cl_2(g) - y \, \text{kJ} \] - This means that converting liquid HCl back to gaseous HCl requires energy, which is absorbed (hence the negative sign). 4. **Compare the Two Reactions**: - Now, we can combine the two reactions: - From reaction (i), we have: \[ H_2(g) + Cl_2(g) \rightarrow 2HCl(g) + x \, \text{kJ} \] - From the reversed reaction (ii): \[ 2HCl(l) \rightarrow H_2(g) + Cl_2(g) - y \, \text{kJ} \] - If we consider the conversion of \( 2HCl(g) \) to \( 2HCl(l) \), we can see that: \[ 2HCl(g) \rightarrow 2HCl(l) \quad \text{(requires heat)} \] - The enthalpy change for this conversion is the difference between the two reactions: \[ x - (-y) = x + y \] 5. **Determine the Relationship**: - The process of converting gas to liquid (condensation) releases heat, so it is exothermic. Therefore, the enthalpy change for converting gaseous HCl to liquid HCl should be positive. - Thus, we can conclude that: \[ x + y > 0 \quad \text{(since heat is released)} \] - This implies that \( y \) must be greater than \( x \) because more energy is required to convert the gaseous HCl back to liquid HCl. 6. **Final Conclusion**: - Therefore, the correct statement is: \[ X < Y \]
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ALLEN-THERMODYNAMICS -EXERCISE -3
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