Q2. For the exothermic reaction PCl 3(g) +Cl 2 (g) <======> PCl 5(gas) Kp=0.160

Question

Q2.

For the exothermic reaction

PCl3(g)+Cl2(g) <======>PCl5(gas)

Kp=0.160 at a certian temperature.

A flask is charged with 0.500 atm PCl3, 0.500 atm Cl2, and .300 atm PCl5 at this temperature.

True or False

__________The net reaction proceeds to the left to attain equlibrium

__________Q is less than k.

__________Q is equal to k.

__________The reaction is at equlibrium

__________Q is greater than k.

___________ No net reaction will occur

____________ The net reaction proceeds to the right to attain equlibrium.

What are the equilibrium partial pressure of PCl3,Cl2, and PCl5 respectively?

Explanation / Answer

2. For the given exothermic reaction,

PCl3 + Cl2 ---> PCl5

Kp = 0.160

With the given concentrations of each reactant and product,

Q = (0.3)/(0.5)(0.5) = 1.2

Which is greater than the Kp value 0.160, therefore,

True : The net reaction proceeds to the left to attain equilibrium [more reactants are formed from product]

False : Q is less than K

False : Q is equal to K

False : The reaction is at equilibrium

True : Q is greater than K

False : No net reaction will occur

False : the net reaction proceeds to the right to attain equilbrium

For the reaction, let x be the change in pressure at equilibrium, then,

Kp = [PCl5]/[PCl3][Cl2]

0.160 = (0.3 - x)/(0.5 - x)(0.5 - x)

0.160 = (0.3 - x)/(0.25 - x + x^2)

0.160x^2 - 0.160x + 0.04 = 0.3 - x

0.160x^2 + 0.84x - 0.26 = 0

x = 0.293 atm

Equilibrium partial pressure of,

PCl3 = 0.5 - 0.293 = 0.207 atm

PCl5 = 0.3 - 0.293 = 0.007 atm

Cl2 = 0.5 - 0.293 = 0.207 atm

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