When heated, hydrogen sulfide gas decomposes according to the equation: 2H2S(g)  2 H2(g) + S2(g) A 3.75 gram sample of H2S(g) is introduced into an evacuated rigid 0.75 L container. The sealed container is heated to 483 K and 2.42 x 10 –2 mol of S2 gas is present at equilibrium. a. Write the expression for the equilibrium constant, Kc, for the reaction above.

Respuesta :

Answer:  [tex]K_c=\frac{(2\times 0.032)^2\times (0.032)}{(0.15-2\times 0.032)^2}[/tex]

Explanation:

Moles of  [tex]H_2S[/tex] = [tex]\frac{\text {given mass}}{\text {molar mass}}=\frac{3.75g}{34g/mol}=0.11mol[/tex]

Volume of solution = 0.75  L

Initial concentration of [tex]H_2S[/tex] = [tex]\frac{moles}{Volume}=\frac{0.11mol}{0.75L}=0.15M[/tex]

Equilibrium concentration of [tex]S_2[/tex] = [tex]\frac{moles}{Volume}=\frac{2.42\times 10^{-2}mol}{0.75L}=0.032M[/tex]

The given balanced equilibrium reaction is,

                            [tex]2H_2S(g)\rightleftharpoons 2H_2(g)+S_2(g)[/tex]

Initial conc.              0.15 M        0        0

At eqm. conc.     (0.15-2x) M   (2x) M   (x) M

The expression for equilibrium constant for this reaction will be,

[tex]K_c=\frac{[H_2]^2\times [S_2]}{[H_2S]^2}[/tex]

Now put all the given values in this expression, we get :

[tex]K_c=\frac{(2x)^2\times (x)}{(0.15-2x)^2}[/tex]

Given : x = 0.032 M

[tex]K_c=\frac{(2\times 0.032)^2\times (0.032)}{(0.15-2\times 0.032)^2}[/tex]

[tex]K_c=0.017[/tex]