Question

Some statements are given for the following equilibrium. \(\mathrm{NH}_{4} \mathrm{HS}(\mathrm{s}) \rightleftharpoons \mathrm{NH}_{3}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{~S}(\mathrm{~g}) ; \Delta \mathrm{H}=+\mathrm{ve}\) \(\mathrm{S}_{1}:\) On increase in temperature, equilibrium pressure of ammonia increases. \(\mathbf{S}_{2}\) : On increase in volume of container at constant temperature, equilibrium pressure of ammonia increases. \(\mathrm{S}_{3}:\) On increase in mass of \(\mathrm{NH}_{4} \mathrm{HS}(\mathrm{s})\) in the container at constant temperature, equilibrium pressure of ammonia increases. (1) \(\mathrm{T} \mathrm{T} \mathrm{T}\) (2) \(\mathrm{F} \mathrm{F} \mathrm{F}\) (3) T T F (4) T F F

Short answer

4) T F F

Step-by-step solution

Analyze Statement S1

Statement S1 states that on increasing the temperature, the equilibrium pressure of ammonia (NH₃) increases. Since \[ \text{∆H} = +\text{ve} \] (endo/exothermic), increasing temperature shifts the equilibrium to the right (Le Chatelier’s principle), producing more gaseous products (NH₃ and H₂S). Hence, S1 is true.

Analyze Statement S2

Statement S2 states that on increasing the volume of the container at constant temperature, the equilibrium pressure of ammonia increases. Increasing the volume decreases the pressure, causing the system to shift to the right to produce more gaseous substances to counter the change. Therefore, S2 is true.

Analyze Statement S3

Statement S3 states that increasing the mass of \[ \text{NH₄HS (s)} \] in the container at constant temperature increases the equilibrium pressure of ammonia. The amount of solid does not affect the equilibrium positions of gases, so change in its mass does not alter the pressure of ammonia. Hence, S3 is false.

Key concepts

Le Chatelier's principle

When a chemical equilibrium experiences a change, it responds to minimize that change. This is Le Chatelier's principle. If you increase the temperature, pressure, or concentration, the system adjusts to counteract the change.
For example, in our given reaction h4hs(s) _RIGHTARROW_ nh3(g) + h2s(g) &Delta H = positiveThe system is endothermic (absorbing heat). When we increase temperature, the system shifts to produce more NH3 and H2S gases (right shift). This increases the equilibrium pressure. This explains why S1 is true.
Key points to remember:

• Increasing temperature in endothermic reactions shifts equilibrium to the right.
• Decreasing temperature shifts equilibrium to the left in endothermic reactions.
• Always consider whether the reaction is endothermic or exothermic.

Endothermic reactions

Endothermic reactions absorb heat from surroundings. They have a positive Delta H value.In the case of h4hs(s) _RIGHTARROW_ nh3(g) + h2s(g), the reaction needs heat to proceed. When we increase the temperature, there’s more heat available. The reaction takes advantage of this by producing more NH3 and H2S. This explains why S1 is correct.

Understanding how endothermic reactions work can explain many equilibrium scenarios:

• Higher temperature favors product formation in endothermic reactions.
• Conversely, lowering temperature will favor the reactants.

Important to note:

• Heat is treated as a reactant in endothermic reactions.
• The system adjusts to counteract temperature changes.

Gas laws

Gas laws describe how gases behave under different conditions. Important examples include:

• Boyle’s law: Pressure inversely affects volume. If volume increases, pressure decreases.
• Charles’ law: Volume is directly proportional to temperature (at constant pressure).
• Avogadro’s law: Volume is proportional to the number of moles of gas (at constant temperature and pressure).

Let's apply Boyle’s law to our scenario (S2). If we increase the container’s volume, pressure decreases, making the system produce more NH3 and H2S to offset this. Hence, S2 is true.

Important points:

• Volume and pressure changes can influence gas equilibrium.
• System shifts to offset volume or pressure changes to maintain equilibrium.