Questions: Given the following mixed-phase reaction at equilibrium: BaF2(s) + 2 H2O(l) ⇌ Ba(OH)2(s) + 2 HF(aq) with ΔrH>0 Indicate the direction will shift after each indicated perturbation. Addition of more solid BaF2: Addition of pure HF: Decrease the temperature of the reaction: Add pure water to dilute the reaction:

Given the following mixed-phase reaction at equilibrium:
BaF2(s) + 2 H2O(l) ⇌ Ba(OH)2(s) + 2 HF(aq) with ΔrH>0

Indicate the direction will shift after each indicated perturbation.

Addition of more solid BaF2:

Addition of pure HF:

Decrease the temperature of the reaction:

Add pure water to dilute the reaction:

Transcript text: Given the following mixed-phase reaction at equilibrium: \[ \mathrm{BaF}_{2}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightleftharpoons \mathrm{Ba}(\mathrm{OH})_{2}(\mathrm{~s})+2 \mathrm{HF}(\mathrm{aq}) \quad \Delta_{\mathrm{r}} \mathrm{H}>0 \] Indicate the direction will shift after each indicated perturbation. Addition of more solid $\mathrm{BaF}_{2}$ : Addition of pure HF: Decrease the temperature of the reaction: Add pure water to dilute the reaction:

Solution

Solution Steps

Step 1: Analyze the Effect of Adding More Solid $\mathrm{BaF}_{2}$

In a heterogeneous equilibrium involving solids and liquids, the concentration of pure solids and liquids does not appear in the equilibrium expression. Therefore, adding more solid $\mathrm{BaF}_{2}$ will not affect the position of the equilibrium.

Step 2: Analyze the Effect of Adding Pure HF

Adding more $\mathrm{HF}$ (a product) will increase its concentration. According to Le Chatelier's principle, the system will shift to counteract this change by favoring the reverse reaction, thus making more reactants.

Step 3: Analyze the Effect of Decreasing the Temperature

The reaction is endothermic ($\Delta_{\mathrm{r}} \mathrm{H} > 0$), meaning it absorbs heat. Decreasing the temperature will shift the equilibrium towards the exothermic direction, which is the reverse reaction, thus making more reactants.

Step 4: Analyze the Effect of Adding Pure Water

Adding more water will dilute the aqueous $\mathrm{HF}$, effectively decreasing its concentration. According to Le Chatelier's principle, the system will shift to increase the concentration of $\mathrm{HF}$ by favoring the forward reaction, thus making more products.