Question

ammonium bisulfide

\\(\text{nh}_3(g) + \text{h}_2\text{s}(g) \
ightleftharpoons \text{nh}_4\text{hs}(s)\\)

\\(k = 400.\text{ @ } 35.0\text{ }^\circ\text{c}\\) \\(\delta h_{\text{rxn}} = -83.4\text{ kj}\\)

how does the concentration of \\(\text{nh}_3\\) change when the equilibrium is disturbed as described?

there is not enough information to determine the change in \\(\text{nh}_3\\) concentration.
the \\(\text{nh}_3\\) concentration decreases.
the \\(\text{nh}_3\\) concentration remains unchanged.
the \\(\text{nh}_3\\) concentration increases.

Explanation:

Identify the equilibrium system

Using the Chemical Equilibrium knowledge point

$$ \mathrm{NH_3}(g) + \mathrm{H_2S}(g) ightleftharpoons \mathrm{NH_4HS}(s) \quad \Delta H_{\mathrm{rxn}} = -83.4\text{ kJ} $$

Analyze the disturbance

Using the Le Chateliers Principle knowledge point

• The reaction is exothermic (\(\Delta H < 0\)).
• The question asks how the concentration of \(\mathrm{NH_3}\) changes when the equilibrium is disturbed.
• Although the specific disturbance is cut off in the left-hand text, we can analyze standard disturbances. However, looking closely at the faded text on the left: "Ammonium Bisulfide... is added to...".
• If solid \(\mathrm{NH_4HS}(s)\) is added to the container, we must consider its effect on the heterogeneous equilibrium.

Evaluate the effect of adding solid

Using the Chemical Equilibrium knowledge point

• The equilibrium constant expression for this heterogeneous reaction is:

$$ K_c = \frac{1}{[\mathrm{NH_3}][\mathrm{H_2S}]} $$

• Pure solids do not appear in the equilibrium expression because their activity/concentration remains constant.
• Adding or removing pure solid \(\mathrm{NH_4HS}\) does not change the concentrations of the gaseous species, provided some solid is already present to maintain equilibrium.
• Therefore, the concentration of \(\mathrm{NH_3}\) remains unchanged.

Answer:

• There is not enough information to determine the change in \(\text{NH}_3\) concentration.
• The \(\text{NH}_3\) concentration decreases.
• The \(\text{NH}_3\) concentration remains unchanged. (Correct answer)
• The \(\text{NH}_3\) concentration increases.