1. finding initial amount.

"At a certain temp, kc= 4.0 for the following rxn;

2HF(g) <=> H2(g) + F2(g)

A 1.0 L rxn vessel contained 0.045 mol of F2(g) at equilibrium. What is the initial amount HF in the rxn vessel?"

I tried doing:

2HF(g) <=> H2(g) + F2(g)

I 0 0.045+x 0.045+x

C +2x -x -x

E +2x 0.045 0.045

4= [0.045][0.045]/[2x]^2

but it didnt work out...the answer is suposed to be HF=0.11mol

2. Combined gas concentration

"solid ammonium carbamate, NH4CO2NH2, decomposes into ammonia gas and carbon dioxide. calculate the value of kc for this system at 40*C if the combined gas concentration at equilibrium is 1.41 x 10^-2 mol/L."

I tried setting it up as:

NH4CO2NH2 <=> 2NH3 + CO2

I 0 7.05x10^-3 +x 7.05x10^-3 +x

C +x -x -x

E +x 7.05x10^-3 7.05x10^-3

im wondering if its correct to divide the "combined gas concentration" equally between the products. and im also stuck because i cant figure out the equilibrium concentration for NH4CO2NH2.