Given the equilibrium system `NH_(4)Cl(s) rarr NH^(+) (aq) + Cl^(-)(aq)`
What change will shift the equilibrium to the right?(`DeltaH = +3.5 kcal//mol`)

Options

A. Decreasing the temperature
B. Increasing the temperature
C. Dissolving NaCl crystals in the equilibrium mixture
D. Dissolving `NH_(4)NO_(3)` crystals in the equilibrium mixture

Explanation

To determine what change will shift the equilibrium of the reaction \( NH_4Cl(s) \rightleftharpoons NH_4^+(aq) + Cl^-(aq) \) to the right, we need to analyze the factors that affect the equilibrium position based on Le Chatelier's principle and the given enthalpy change (\( \Delta H = +3.5 \, \text{kcal/mol} \)).

### Step-by-Step Solution:

1. **Identify the Nature of the Reaction**:
- The reaction involves the dissolution of solid ammonium chloride (\( NH_4Cl \)) into its ions (\( NH_4^+ \) and \( Cl^- \)).
- Since \( \Delta H \) is positive, this reaction is endothermic, meaning it absorbs heat.

2. **Effect of Temperature**:
- According to Le Chatelier's principle, if we increase the temperature of an endothermic reaction, the equilibrium will shift to the right to absorb the added heat.
- Therefore, increasing the temperature will favor the formation of products (\( NH_4^+ \) and \( Cl^- \)).

3. **Effect of Concentration**:
- Adding more of a reactant or removing a product will shift the equilibrium to the right.
- However, in this case, since \( NH_4Cl \) is a solid, its concentration does not affect the equilibrium position.

4. **Effect of Adding Ions**:
- If we add a salt like \( NaCl \) to the solution, it dissociates into \( Na^+ \) and \( Cl^- \). This increases the concentration of \( Cl^- \) in the solution.
- According to the reaction quotient \( Q \), if the concentration of products increases, the equilibrium will shift to the left to counteract this change. Therefore, adding \( NaCl \) will not shift the equilibrium to the right.

5. **Conclusion**:
- The only change that will shift the equilibrium to the right is increasing the temperature.

### Final Answer:
To shift the equilibrium to the right, **increase the temperature**.

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