[lucasloredo]

I'm not sure even where to start on this problem:

given the equation     2NaHCO₃ (s) <--------->  Na₂CO₃ (s) + H₂O (g) + CO₂ (g)

A sample of 100. grams of solid NaHCO₃ was placed in a previously evacuated rigid 5.00 liter container and heated to 160 degrees C. Some of the original solid remained and the total pressure in the container was 7.76 atmospheres when equilibrium was reached. Calculate the number of moles of H20 (g) present at equilibrium.

I tried using K_p and partial pressures but I haven't done enough of these kind of problems to know what to do. Thanks in advance!

[Borek]

Gas produced is an equimolar mixture of CO₂ and H₂O - so H₂O is exactly half of it.

[lucasloredo]

yes that is what I was thinking, which would make the pressure of the H₂O gas at 3.75 atm.

Ah, now I understand, so after finding its pressure you use the formula PV = nRT to find the moles . . . gotcha

Thanks!