IIT JEE Chemistry Problems in Le Châtelier’s Principle topic in Chemical Equilibrium concepts And Their Solutions with Detailed Step by Step Explanation.
This section includes many important IIT JEE Chemistry problems in Chemical Equilibrium topics that are considered to be very important from IITJEE exam point of view. Here the solutions for these problems are very detailed with explanation for each step. This section is very helpful for students to get very high scores in IIT JEE mains and advanced.
Chemical Equilibrium – Le Châtelier’s Principle
If a system at equilibrium is subjected to a change in temperature , pressure (or) concentration the equilibrium position shifts.
Le Châtelier’s Principle: This “shift” is governed by Le Châtelier’s Principle, which states: “If a change of condition (stress) is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.”
Common “stresses” that cause a shift include:
- Change in Concentration:
- Adding more reactant: The equilibrium shifts to the right (products) to consume the added reactant.
- Removing a product: The equilibrium shifts to the right (products) to replenish the removed product.
- Change in Pressure/Volume (for gaseous reactions):
- Increasing pressure (decreasing volume): The equilibrium shifts towards the side with fewer moles of gas to reduce the pressure.
- Decreasing pressure (increasing volume): The equilibrium shifts towards the side with more moles of gas to increase the pressure.
- Change in Temperature:
- Increasing temperature:
- For endothermic reactions (absorb heat, heat is a “reactant”): Shifts to the right (products).
- For exothermic reactions (release heat, heat is a “product”): Shifts to the left (reactants).
- Decreasing temperature:
- For endothermic reactions: Shifts to the left (reactants).
- For exothermic reactions: Shifts to the right (products).
- Increasing temperature:
🟩 Problem 1:
When NaNO₃ is heated in a closed vessel, oxygen is liberated and NaNO₂ is left behind at equilibrium. Then:
Options:
- Addition of NaNO₂ favours forward reaction.
- Addition of NaNO₃ favours forward reaction.
- Increasing of temperature favours forward reaction.
- Both addition of NaNO₃ and increasing of temperature favour forward reaction.
Answer: (4) Both addition of NaNO₃ and increasing temperature favour forward reaction
Explanation:
Heating NaNO3 in closed vessel liberates O2 \( \ce{2NaNO3 ⇌ 2NaNO2 + O2} \)
🟩 Problem 2:
The dissociation of CaCO₃ takes place as per the equation CaCO₃(s) ⇌ CaO(s) + CO₂(g); ΔH = +178 kJ. If the reaction is carried out in a closed vessel, the pressure of CO₂ increases and reaches a constant value when
Options:
- Temperature is increased.
- Temperature is decreased.
- Volume of vessel is increased.
- Amount of CaCO₃ is decreased.
Answer: (1) Temperature is increased
Explanation: Endothermic decomposition is favored by heat. Also, CO₂ pressure increases until equilibrium is restored.
🟩 Problem 3:
Le Chatelier’s principle not applicable to which of the following?
Options:
- \( \ce{2SO2 + O2 <=> 2SO3} \)
- \( \ce{Fe(s) + S(s) <=> FeS(s)} \)
- \( \ce{N2 + 3H2 <=> 2NH3} \)
- \( \ce{N2 + O2 <=> 2NO} \)
Answer: (2)
Explanation: All substances in (2) are solids. Pressure/temperature changes don’t shift equilibrium — LCP doesn’t apply.