A sample of HI(g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI(g) is 0.04 atm. What is Kp for the given equilibrium?

2HI (g) ⇌H2 (g) + I2 (g)

Partial pressure of HI = 0.04 atm

sum of partial pressures = total pressure,


thus,


P(H2)+P(I2)= P – P(HI)


Where,


P is total pressure = 0.2 atm


P(H2) is Partial pressure of H2 = x


P(I2) is Partial pressure of I2= x


P(HI) is Partial pressure of HI = 0.04 atm


∴ x + x = 0.2 – 0.04


= 0.16


i.e, x = 0.08 atm


Kp=


= = 4


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