I am to do an equilibrium constant lab and I am supposed to only find the Kc value. i have to find the equilibrium constant for NaHCO3 (s) NaOH (s) + CO2 (g) at 800K. The partial pressure in the bulb reads 420 kPa on the manometer, 1 gram of NaHCO3 was added to the bulb and the bulb's volume is 500 mL.

Question

I am to do an equilibrium constant lab and I am supposed to only find the Kc value. i have to find the equilibrium constant for NaHCO3 (s) <--> NaOH (s) + CO2 (g) at 800K. The partial pressure in the bulb reads 420 kPa on the manometer, 1 gram of NaHCO3 was added to the bulb and the bulb's volume is 500 mL.

I'm not sure if I did this correct but I used the PV=nRT formula and solved for n and I got 0.00316 mols. Then I used the c=n/v formula to find the concentration, and i got 6.3x10^-6. I don't know where to go from here to find the Kc value.

DrBob222 · Answer

I think you've made two errors in calculation. If I use 420 kPa and 0.5 L volume with T 800K I solve for n = PV/RT and I obtained your value x 10. Then if I use c = n/v that's n/0.5L = Your value divided by 1000. I think your data are good; I think your calculations need work. If I didn't goof I found n = 0.03157; then
c = n/0.5 = 0.063148 which I would round to 0.0632.
Kc = (CO2)
Then for the fun of it convert Kc = 0.0632 to Kp and see if you get 420 kPa.