How do I do this chemistry problem?

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Brian

New member
Nitrosyl bromide decomposes according to this chemical equation: 2NOBr(g)<--->2NO(g) + Br2(g). When 0.500 atm of NOBr is sealed in a flask and allowed to reach equilibrium, 18% of the NOBr decomposes. Calculate the equilibrium constant, Kp, for the reaction.

Will somebody please help me figure out how to do this? I promise to award 10 points.
 
2NOBr(g) <---> 2NO(g) + Br2(g)
number of moles at equilibrium (n) 2(1-x) 2x x

n = 2(1-x) + 2x + x = 2 +x

where x is the degree of dissociation

partial pressure of NOBr = 2(1-x) P/2+x

partial pressure of NO = (2x) P/ 2+x

and partial pressure of Br = xP/2+x

Kp = (partial pressure of NO)^2 x partial pressure of Br/(partial pressure of NOBr)^2

Kp = [ (2x) P/ 2+x]^2 (xP/2+x) / [2(1-x) P/2+x ]^2

Kp = x^3 P/ [(2 +x) (1-x)^2]

total pressure is given that is 0.500 atm
and degree of dissociation is also given that is 18% = 0.18

now let's plug in the values in the relation what we have got so far.

Kp = (0.18)^3 (0.500)/(2+0.18) (1 - 0.18)^2

Kp = 0.002916/1.4658

Kp = 0.00198 = 1.98 x 10^-3 atm
 
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