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Postby melodyzaki2E » Tue Jan 08, 2019 7:47 pm

A 25.0-g sample of ammonium carbamate, NH4(NH2CO2), was placed in an evacuated 0.250-L fl ask 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).

Why cant you convert the moles of NH4(NH2CO2) to moles of NH3, why do you have to use the moles of CO2?

Matthew Tran 1H
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Re: 11.41

Postby Matthew Tran 1H » Tue Jan 08, 2019 8:47 pm

You have to use the moles of CO2 present at equilibrium to find the moles of NH3 at equilibrium and to find the moles of ammonium carbamate consumed using mole ratios. You can't use the initial moles of ammonium carbamate since the reaction does not proceed to completion (it's in equilibrium); that is, not all the ammonium carbamate is consumed in the reaction. After you find the moles of reactants and products at equilibrium, you then convert to concentrations to find the value of Kc. You can also convert moles to concentration in the beginning and follow the same steps.

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