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1. The equilibrium pressures for reaction of decomposition of N 2 O 4 to 2 NO 2

ID: 794934 • Letter: 1

Question

1.     The equilibrium pressures for reaction of decomposition of N2O4 to 2 NO2 are 0.58 bar and 1.6 bar respectively at room temperature. If the volume of the container is reduced by a factor of 2 at constant temperature, what would be the partial pressure of the gases when the equilibrium is re-established? (assume ideal behavior)

PLEASE SHOW ALL RELEVANT EQUATIONS AND WORK THE EQUATION FIRST, SO I CAN SEE HOW IT IS DONE! I have a hard time with the algebra, and would like to learn how to work that in the equation. Thank you!

The equilibrium pressures for reaction of decomposition of N2O4 to 2 NO2 are 0.58 bar and 1.6 bar respectively at room temperature. If the volume of the container is reduced by a factor of 2 at constant temperature, what would be the partial pressure of the gases when the equilibrium is re-established?

Explanation / Answer

Equilibrium equation

N2O4(g) ---> 2NO2(g)

Kp = p2NO2 / pN2O4

Kp = (1.6)2 / 0.58 = 4.414

Kp = 4.414

The value of Kp will remain constant as the temperature is kept constant

The total pressure = Partial pressure of NO2 + Partial pressure of N2O4

total pressure = 1.6 +0.58 = 2.18 atm

if we halved the volume at constant temperature , the pressure will become double

So the total pressure = 2 X 2.18 = 4.36 atm

            N2O4(g) --->   2NO2(g)  

Initial        0.58            1.6

Change    -x               +2x

Equilibr    0.58-x       1.6 +2x

Kp = 4.414 = (Partial pressure of NO2)^2 / Partial pressure of N2O4

The reaction will be [we have decreased the volume so system will move in backward direction]

           N2O4(g) ---> 2NO2(g)

Initial     1.16              3.2

Change +x             -2x

Equilibr   1.16+x        3.2-2x

K = 4.414 = (3.2-2x)^2 / (1.16+x)

4.414(1.16+x) = 10.24 + 4x2 - 4x

5.12 + 4.414x = 10.24 + 4x2 - 4x

x = 0.321

pressure of NO2 = 3.2-2(0.321) = 2.56 atm

Pressure of N2O4 = 1.16 + 0.321 = 1.481atm