To determine whether the reaction will shift left, right, or remain unchanged upon each disturbance, we need to analyze the effect of the disturbance on the equilibrium of the hydrofluoric acid dissociation reaction.
The dissociation reaction of hydrofluoric acid (HF) in water can be represented as:
HF(aq) ⇌ H+(aq) + F-(aq)
1. Add solid sodium fluoride:
By adding solid sodium fluoride (NaF), which is a salt consisting of Na+ and F- ions, we are increasing the concentration of F- ions in the solution. According to Le Chatelier's principle, an increase in the concentration of one of the products (F-) will cause the equilibrium to shift toward the reactants to counterbalance the change. Therefore, the reaction will shift left.
2. Add solid sodium hydroxide:
Adding solid sodium hydroxide (NaOH) introduces OH- ions into the solution. These hydroxide ions will react with the H+ ions from the dissociation of HF, forming water molecules. This reaction consumes H+ ions, causing the equilibrium to shift right to produce more H+ ions. Hence, the reaction will shift right.
3. Add a drop of concentrated hydrochloric acid:
Concentrated hydrochloric acid (HCl) is a strong acid that completely dissociates in water. Adding a drop of HCl will increase the concentration of H+ ions in the solution. This increase of H+ ions will cause the equilibrium to shift left to counterbalance the change. Thus, the reaction will shift left.
4. Add solid iron(III) hydroxide:
Solid iron(III) hydroxide (Fe(OH)3) is an ionic compound that does not contribute to the concentration of H+ or F- ions in solution. Therefore, the presence of solid iron(III) hydroxide will not affect the equilibrium of the reaction. The reaction will remain unchanged.
5. Add solid sodium nitrate:
Solid sodium nitrate (NaNO3) dissociates completely in water, forming Na+ and NO3- ions. Since neither Na+ nor NO3- ions have any effect on the concentration of H+ or F- ions, the equilibrium of the reaction will not be affected. The reaction will remain unchanged.
6. Add solid Barium fluoride:
Adding solid barium fluoride (BaF2), a salt consisting of Ba2+ and F- ions, does not affect the concentration of H+ or F- ions in solution. Therefore, the equilibrium of the reaction will remain unchanged.
7. Add water:
Adding water to the system will change the total volume but will not affect the concentration of the existing H+ or F- ions. Consequently, the equilibrium of the reaction will not be affected. The reaction will remain unchanged.
In summary:
- Add solid sodium fluoride: Shift left
- Add solid sodium hydroxide: Shift right
- Add a drop of concentrated hydrochloric acid: Shift left
- Add solid iron(III) hydroxide: No change
- Add solid sodium nitrate: No change
- Add solid barium fluoride: No change
- Add water: No change