Chemistry - Chemical Equilibrium Question with Solution | TestHub
Gaseous nitrosyl bromide (NOBr) and Ar are taken in a flask, sealed and heated to some temperature where the total pressure would have been 1.0 bar had not the following equilibrium been established
2NOBr(g) ⇌ 2NO(g) + Br2(g)
But the actual pressure was found to be 1.1 bar. Now, into the equilibrium mixture, some Br2 gas was introduced at constant volume and temperature so that the total pressure would have been 1.675 bar had no further reaction occurred but the actual pressure was found to be 1.625 bar. The equilibrium constant, KP (in bar), for the decomposition reaction under the given experimental condition is (Answer by multiplying the KP value with 1000)
Answer:
Solution:
Let initial pressures be NOBr = a and Ar = 1.0 - a bar First equilibrium: pressure rise = 1.1 - 1.0 = 0.1 bar, so PBr2 = 0.1, PNO = 0.2, PNOBr = a - 0.2
KP = (0.2)2(0.1)/(a-0.2)2 = 0.004/(a-0.2)2
Br2 added = 1.675 - 1.1 = 0.575 bar
Backward reaction by w: pressure falls by w = 1.675 - 1.625 = 0.05 bar
Second equilibrium: PNO = 0.2 - 0.1 = 0.1, PBr2 = 0.1 + 0.575 - 0.05 = 0.625, PNOBr = a - 0.2 + 0.1 = a - 0.1
KP = (0.1)2(0.625)/(a-0.1)2 = 0.00625/(a-0.1)2
Equating: (a-0.1)2 = 1.5625(a-0.2)2, so a - 0.1 = 1.25(a - 0.2) and a = 0.6 bar
KP = 0.004/(0.4)2 = 0.025 bar
1000KP = 25, written as 0025
