In an experiment, at a total pressure of 10atm and 400 degree celcius, the equilibrium mixture 2NH3=N2+3H2 the ammonia was found to have dissociated to the extent of 96%. Calculated Kp for the rxn. (reversible rxn).
Set up an ICE chart with P = pressure NH3 initially. Total P at equilibrium is 10 atm. If it is 96% dissociated, then you lose 0.96P NH3, form 1/2 that for N2 and form 3/2 that for H2.
...........2NH3 ==> N2 + 3H2
I...........P......0......0
C........-0.96P...0.48P..1.44P
E.........0.04P..0.48P...1.44P
Total P = pNH3 | pN2 + pH2
10 = 0.04p + 0.48P + 1.44P
10 = 1.96p
p = 10/1.96 = about 5 but you need it more accurate than that.
Calculate pressure of each and substitute into Kp expression to solve for Kp.
To calculate the equilibrium constant (Kp) for the reversible reaction 2NH3 ⇌ N2 + 3H2, we need to use the given information about the extent of dissociation of ammonia (NH3). Let's break down the steps to solve the problem:
Step 1: Write the balanced equation for the reaction.
2NH3 ⇌ N2 + 3H2
Step 2: Write down the expression for Kp.
Kp = (PN2)(PH2)^3 / (PNH3)^2
Step 3: Find the partial pressures of each species at equilibrium.
Given that ammonia (NH3) has dissociated to the extent of 96%, we can assume that 96% of the original ammonia has dissociated. Therefore, the concentration of NH3 at equilibrium will be 4% of its initial concentration.
Step 4: Calculate the mole fraction of each species.
Since we know the total pressure (Ptotal = 10 atm) and the partial pressure of NH3 (PNH3), we can calculate the mole fraction of NH3 as follows:
PNH3 = (mole fraction of NH3) × Ptotal
Step 5: Substitute the values into the expression for Kp.
Since we know the mole fractions for NH3, N2, and H2, we can substitute the values into the equation obtained in Step 2 and calculate Kp.
It's important to note that the given temperature (400 degrees Celsius) is required to convert the partial pressures to mole fractions using the ideal gas law.