Chemistry Equilibrium (Can Someone Answer This)

Question

Consider the reaction 2NOCl_(g) —> 2NO_(g) + Cl_2(g). At 25^oC, a particular experiment showed the equilibrium pressures to be

PCl₂ = 3.00 E^-3 atm

PNO_(g) = 1.25 E^-3 atm

PNOCl_(g) = 1.20 atm

a. Calculate K_p

b. In another experiment involving the same reaction and conditions, the container initially contains the following partial pressures:

PCl₂ = 3.00 E^-3 atm

PNO_(g) = 2.00 E^-3 atm

PNOCl_(g) = 1.50 atm

Predict whether the partial pressure of Cl_2(g) wil increase, decrease, or stay the same as the system approaches equilibrium. Justify your prediction with a calculation.

Answer 1

a) The K_P expression is P_Cl2P_NO²/ P_NOCl² Just input the values at equilibrium to find the K_P

b) Plug in the given initial values into the K expression; this is usually called Q:

If Q > K backward reaction dominates

if Q = K equilibrium

if Q < K forward reaction dominates

The K here is the one from (a)

Good Luck!

Answer 2

Hello, Elijah,

a.) From the balanced equation we can write the calculation for K_p:

K_p = ([NO]²[Cl₂])/[NOCl]²

For calculating the K_p, we can use the partial pressures of the gases for their concentrations. So enter the 3 values for partial pressures and solve for K_p.

K_p = ([1.25x10^-3]² [3x10^-3])/[1.2]

K_p = 3.26 x10^-9 with 3 sig figs. Check my calculation to be sure it is correct.

b.) We are asked what will happen to the partial pressure of Cl₂ under a new set of conditions. We'll assume the K_p we calculated above is correct, and compare it to the result we get from doing the same calculation but using the new partial pressures.

Substitute the new partial pressures into the same equation and calculate the resulting "effective" K_p. I get a value of 5.33x10^-9. This is higher than the actual K_p, so something must change to bring the number down, closer to 3.26x10^-9. By looking at the original relationship, we see that [Cl₂] appears in the numerator. So either it or the [NOCl] (or both) must decline. Absent any change in the NOCl partial pressure, we must conclude that the [Cl₂] partial pressure must decline, so that the calculation moves closer to the true K_p.

I hope this helps,

Bob