We’re being asked to **determine the partial pressure of Ammonia when 250 g of NH4I is placed in a 3 L flasked heated up to 300°C**

NH_{4}I(s) ⇋ NH_{3}(g) + HI(g)

Recall that the ** equilibrium constant** is the ratio of the products and reactants. We use

$\overline{){{\mathbf{K}}}_{{\mathbf{p}}}{\mathbf{=}}\frac{{\mathbf{P}}_{\mathbf{products}}}{{\mathbf{P}}_{\mathbf{reactants}}}}$ $\overline{){{\mathbf{K}}}_{{\mathbf{c}}}{\mathbf{=}}\frac{\mathbf{\left[}\mathbf{products}\mathbf{\right]}}{\mathbf{\left[}\mathbf{reactants}\mathbf{\right]}}}$

Note that __solid and liquid compounds are ignored in the equilibrium expression.__

Ammonium iodide can dissociate to produce HI and ammonia, NH_{4}I(s) ⇌ NH_{3}(g) + HI(g). At 300 °C, K_{p} = 0.42. If 250. g of ammonium iodide is placed into a 3.00 L flask and heated to 300 °C, what is the partial pressure of ammonia at equilibrium?

a. 0.84 atm

b. 0.21 atm

c. 0.42 atm

d. 0.65 atm

e. 0.18 atm