1.) For the reaction: 2Br (g) -> Br 2(g) Kp=0.0004 at 4000K. What is the value o

Question

1.) For the reaction: 2Br(g) -> Br2(g)

Kp=0.0004 at 4000K. What is the value of Kc at the same temperature?

What is the equilibrium concentration of Br2 if the reaction was started with 1mol of Br2 in1L chamber

when it reaches the equilibrium?

2.) Consider the reaction N2O4(g)2NO2(g) that occurs in a 1L vessel.

At the start of the reaction a 2:5 molar ratio mix of N2O4 and NO2 was present. What is the Qc of the reaction?

Once the system is at equilibrium, the Kc of the reaction was found to be 10.2. Which direction would the equilibrium shifts to, starting from the initial 2:5 mixture judging by your previously calculated Qc?

What is the equilibrium ratio between of N2O4 and NO2?

Explanation / Answer

1) Kc = Kp/(RT)^dn

with,

Kp = 0.0004

dn = 1 - 2 = -1

R = 0.0821 L.atm/K.mol

T = 4000 K

we get,

Kc = 0.0004 x (0.0821 x 4000) = 0.131

2) Qc for the reaction would be,

Qc = [NO2]^2/[N2O4]

with,

[NO2] = 5 mol/1 L = 5 M

[N2O4] = 2 mol/1 L = 2 M

we get at the start,

Qc = (5)^2/2 = 12.5

At equilibrium, Kc = 10.2

Kc has decreased, so the product amount has gone down. The direction of equilibrium shift is towards reactants.

Equilibrium ratio of N2O4 and NO2 is,

[N2O4]/[NO2]^2 = 1/10.2 = 0.098

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