Chemistry help?? I need a head start?

Question

At 275 oC, the equilibrium constant for the reaction below is 1.04 x 10-2

NH4Cl (s) ó NH3 (g) + HCl (g)

A 0.980 g sample of the solid NH4Cl is placed in a 1.000 L closed container and heated to 275 oC.

So i began this problem using Gr= Gr(standard) + RTlnQ, attempting to find Gr. but the units are different

Then I tried put two equations together. Gr=RTlnK+RTlnQ to find Q but i don't know Gr.

So how do you find Q for (a) ??

i've been stuck on whole problem for like 2 days. Please help me with this problem.

a) Will there be any decomposition of the NH4Cl when the system comes to equilibrium at 275 oC? (Compare Q to K)

b) At equilibrium what will the partial pressures of the products and the total pressure of the gases inside the container?

c) What will be the mass of solid NH4Cl in the container at equilibrium?

So i began this problem using Gr= Gr(standard) + RTlnQ, attempting to find Gr. but the units are different

Then I tried put two equations together. Gr=RTlnK+RTlnQ to find Q but i don't know Gr.

So how do you find Q for (a) ??

i've been stuck on whole problem for like 2 days. Please help me with this problem.

Answer 1

If you haven't figured it out yet maybe this can help:

I started with Gr first too, and turns out I don't need it.

To find Q use the activities of the gases. The gases are 0 since there aren't any there and whenever a solid is involved it's activity is 1. so you end up with 0x0/1 = 0 which is < K so you can say it does decompose.

Then set up the equation in an I.C.E table, and convert K to Kc. Use Kc to solve for X. Remember the solid will not appear, it will just be a 1 in the denominator.

from there you can work the rest out pretty easily.