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An equal number of moles of I2(g) and Br2(g) are placed into a closed container and allowed to establish the following equilibrium:


I2(g) + Br2(g) 2IBr(g)


Keq = 280


Which one of the following relates [IBr] to [I2] at equilibrium?





[I2] = [IBr]





[I2] < [IBr]





[I2] = 2 [IBr]





[I2] = 280 [IBr]

Verified Answer :

B. I'm in the same class

Answer : The correct option is, \([I_2]<[IBr]\)

Solution : Given,

Moles of \(I_2\) = Moles of \(Br_2\)

\(K_{eq}=280\)

The balanced equilibrium reaction is,

\(I_2(g)+Br_2(g)\rightleftharpoons 2IBr(g)\)

The expression for equilibrium constant is,

\(K_{eq}=\frac{[IBr]^2}{[I_2][Br_2]}\)

As per question, Moles of \(I_2\) = Moles of \(Br_2\)

Now put all the given values in above formula, we get the relation between the \([IBr]\) and \([I_2]\).

\(280=\frac{[IBr]^2}{[I_2][I_2]}\)

\(280=\frac{[IBr]^2}{[I_2]^2}\)

\(\sqrt{280}=\frac{[IBr]}{[I_2]}\)

\([IBr]=16.733\times [I_2]\)

From this we conclude that the concentration of \(IBr\) is greater than the concentration of \(I_2\).

Therefore, the correct option is, \([I_2]<[IBr]\)