ICE Chart for HW problem 11.49 6th Edition

[KarlaArevalo2F]

How would one understand to complete an ICE chart for problem 11.49? I have gotten the initial for NH3 but how would we know what steps to follow after? (First time seeing ICE charts :( )

[Kate Chow 4H]

Since you know that NH4HS is a solid, you can put 0 in for the whole column. You can add "x" to both NH3 and H2S in the change row (C) because you eventually want to find their equilibrium concentrations. You're given Kc so you can use the equilibrium equation: Kc=[NH3][H2S]. Kc=[0.2+x][x]. Solve for x using the quadratic formula and you have your answer!

NH4HS ---> NH3 + H2S
I 0, .4mol/2L, 0

C 0, +x, +x

E 0, 0.2M+x, +x

Hope this helps! (the formatting got weird when I posted, but hopefully you can still understand the ice table)

[KarlaArevalo2F]

thank you for your explanation! My point of confusion is using the quadratic formula in the chart. May you please explain..

[Vincent Li 4L]

In this case, you would use the quadratic equation on what Kate pointed out to be the equilibrium constant expression, Kc = [0.2 + x][x]. Since you have one variable, x, and there is no other way to properly factor it, once you expand out the Kc expression, you use the quadratic formula x = (-b ± √(b^2 - 4ac))/(2a). Solving for x will give you two possible answers, so be sure to eliminate any that are either negative (not possible to have negative partial pressure or concentrations) or any that exceed the initial values.

[KarlaArevalo2F]

Thank you both!