5I.33

keyaluo4C
Posts: 54
Joined: Fri Sep 28, 2018 12:17 am

5I.33

The question is:
A sample of ammonium carbamate, NH4(NH2CO2), of mass 25.0 g was placed in an evacuated flask of volume 0.250 L and kept at 25 °C. At equilibrium, 17.4 mg of CO2 was present. What is the value of Kc for the decomposition of ammonium carbamate into ammonia and carbon dioxide? The reaction is
NH4(NH2CO2)(s)⇌2 NH3(g) + CO2(g)

In the answer key, the molar concentration of CO2 is 1.581 mol/L but when I calculate I get 0.00158 mol/L.

What am I doing wrong here?

605168557
Posts: 65
Joined: Fri Sep 28, 2018 12:18 am

Re: 5I.33

Did you make sure to convert the 17.4 mg to 0.0174 g CO2? Also when finding the Kc you should be dividing the concentrations of [NH3]^2 and [CO2} by 0.250 not the 25.0 g amount given in the question.

605168557
Posts: 65
Joined: Fri Sep 28, 2018 12:18 am

Re: 5I.33

Did you make sure to convert the 17.4 mg to 0.0174 g CO2? Also when finding the Kc you should be dividing the concentrations of [NH3]^2 and [CO2} by 0.250 not the 25.0 g amount given in the question.