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5I.33

Posted: Sat Mar 16, 2019 1:50 am
by keyaluo4C
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?

Re: 5I.33

Posted: Sat Mar 16, 2019 12:10 pm
by 605168557
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.

Re: 5I.33

Posted: Sat Mar 16, 2019 12:11 pm
by 605168557
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.