CaCO,(s) CaO(G) + CO,(8) 4. When heated, calcium carbonate decomposes according
ID: 1039961 • Letter: C
Question
CaCO,(s) CaO(G) + CO,(8) 4. When heated, calcium carbonate decomposes according to the equation above. In 3 study of the decomposition of calcium carbonate, a student added 50.0 gxample of powdered CaCO,()to1.00 L pigid container. The student sealed the container, pumped out ait the gases, then heated the container in an oven at 1100 K. As the container was heated, the total pressure of the CO2(8) in the container was measured over time. The data are plotted in the graph below. 1.25 1-123 1.00 0.75 0.50 0.25 0 15 20 10 Time (min) 0 The student repeated the experiment, but this time the student-used 100.0 le of powdered CaCO(s). In this experiment, the final pressure in the container was 1.04 atrm, first experiment. hich was the same final pressure as in the (e) Calculate the number of moles of CO,(e) present in the container after 20 minutes of heating (tb) The student claimed that the final pressure in the container in each experiment became constant because all of the CaCO,(0) had decomposed. Based on the data in the experiments, do you agree with this claim? Explain. (c) After 20 minutes some CO (8) was injected into the container, initially raising the pressure to 1.5 atm Would the final pressure inside the container be less than, greater than, or equal to 1.04 atm? Explain your reasoning. (d) Are there sufficient data obtained in the experiments to determine the value of the equilibrium constant, Kp for the decomposition of CaCO,(s) at 1100 K? Justify your answer.Explanation / Answer
Ans> Final Pressure P= 1.04 atm ; Volume V = 1L ; Temperature T = 1100K ; Gas Const R = 0.082 Latm mole-1K-1. We know from ideal gas equation that, PV =nRT
a) Putting the values in ideal gas equation we get, n = (1.04 x 1)/(0.082 x 1100) = 0.12 moles of CO2 is present in the container.
b) No all the calcium carbonate has not been decomposed. The value of equillibrium constant remains const for a particular temperature. Kp = {pCO2} since the rest are solid that is Calcium carbonate reactnat and calcium oxide are solid and hence their concentration are unity. So in the equillibrium const expression only the pCO2 is the determining factor. As in both the cases we heat the container upto 1100K so in both these cases the Kp is same which implies that 0.12 moles of carbondioxide is produced in both the cases. The reaction is an equillibrium so there is some unreacted calcium caronate present.
c) According to Le-Chatliers principle which states the when a system at equillibrium is subjected to a change in concentration then the system readjusts itself to counteract the change and a new equillibrium is established keeping the value of equillibrium constant same. So the final pressure inside the container would remain same equall to 1.94 atm. Some of the added CO2 will react with CaO to form calcium carbonate that is there will be a backward shift in the equillibrium if CO2 is injected into the system externally.
d) Yes. The data is sufficient. All other recatant and product other than CO2 being solid will not appear in the Kp expressio and Kp will be only pCO2 that is = 0.12