A sample of NH4HS(s) is placed in a 2.61 −L flask containing 0.120 mol NH3(g).
NH4HS(s)⇌NH3(g)+H2S(g) Kp=0.108 at 25∘C
Part A
What will be the total gas pressure when equilibrium is established at 25∘C?
I'm getting P = 1.21atm which is wrong.
Can any1 please help. Thanks
A sample of NH4HS(s) is placed in a 2.61 −L flask containing 0.120 mol NH3(g).
NH4HS(s)⇌NH3(g)+H2S(g) Kp=0.108 at 25∘C
Part A
What will be the total gas pressure when equilibrium is established at 25∘C?
I'm getting P = 1.21atm which is wrong.
Can any1 please help. Thanks
Use PV = nRT and solve for p. That's approx 1.12 but you need a more accurate answer than that.
........NH4HS ==> NH3 + H2S
I.......solid.....1.12....0
C......solid.......+p....+p
E......solid.....1.l2+p...p
Write the expression for Kp, substitute the E line into Kp expression, solve the quadratic for p, then Ptotal = 1.12 + p + p = approx 1.31
WRONG
To find the correct answer, we need to use the equilibrium constant expression and the given information.
Given:
Kp = 0.108
Initial moles of NH3(g) = 0.120 mol
Step 1: Write the balanced equation for the reaction:
NH4HS(s) ⇌ NH3(g) + H2S(g)
Step 2: Set up an ICE table (Initial, Change, Equilibrium) to organize the information. Assume x mol of NH3(g) and H2S(g) are formed at equilibrium.
NH4HS(s) ⇌ NH3(g) + H2S(g)
Initial: 0 0.120 0
Change: -x +x +x
Equilibrium: 0-x 0.120+x 0+x
Step 3: Use the ideal gas law to relate the partial pressure of NH3(g) to its molar amount:
P(NH3) = (n(NH3)RT)/V
where P is the pressure, n is the number of moles, R is the ideal gas constant (0.0821 L·atm/(mol·K)), T is the temperature in Kelvin, and V is the volume.
P(NH3) = (0.120 mol * 0.0821 L·atm/(mol·K) * 298 K) / 2.61 L
= 2.238 atm
Step 4: Use the equilibrium constant expression to set up the equation:
Kp = (P(NH3) * P(H2S)) / P(NH4HS)
Substitute the values:
0.108 = (2.238 * P(H2S)) / (0.120 - x)
Since x is negligible compared to 0.120, we can approximate the equation to:
0.108 = (2.238 * P(H2S)) / 0.120
Step 5: Rearrange the equation and solve for P(H2S):
P(H2S) = (0.108 * 0.120) / 2.238
= 0.0058 atm
Step 6: Calculate the total gas pressure at equilibrium by summing the individual pressures:
Total pressure = P(NH3) + P(H2S)
= 2.238 atm + 0.0058 atm
= 2.2438 atm or approximately 2.24 atm
Therefore, the correct total gas pressure when equilibrium is established is approximately 2.24 atm.