Sodium carbonate, Na2CO3(s), can be prepared by heating sodium bicarbonate, NaHCO3(s).

Question

2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) Kp = 0.34 at 160 ºC
If a sample of NaHCO3 is placed in an evacuated flask and allowed to achieve equilibrium at 100 ºC, what will the total gas pressure be?

Answer 1

Did you make typo? If Kp is at 160 C then it will be different at 100 C. Assuming you mean Ptotal at 160 C...
....2NaHCO3(s)=>Na2CO3(S)+CO2(g)+H2O(g)
I...solid.......solid......0......0
C...solid.......solid......p......p
E...solid.......solid......p......p

Kp = pCO2 * pH2O
Substitute the E line into Kp expression and solve for p. Then total P is 2p.