Question

Consider: $H_2\left(g\right)+B{r}_2\left(g\right)\rightleftharpoons 2HBr\left(g\right)$ The concentrations of $H_2,B{r}_2$ and $HBr$ are $0.05M,0.03M,$ and $500.0M$. The equilibrium constant for this reaction at ${400}^{\circ }C$ is $2.5\times {10}^3$. Is this system at equilibrium?

• A. Yes, the system is at equilibrium
• B. No, the reaction must shift to the right in order to reach equilibrium
• C. No, the reaction must shift to the left in order to reach equilibrium
• D. It cannot be determined
• E. The reaction will never be at equilibrium

Answer 1

The correct option is C No, the reaction must shift to the left in order to reach equilibrium

According to lechatelier principal equilibrium constant

$K$$=$$\left[HBr{]}^2/\right(\left[H_2\right]\ast \left[B{r}_2\right])$

so $K=$$(500\ast 500)/(.05\ast .03)$$=$$1.66\ast {10}^8$

but given that equilibrium constant $K_C$$=$$2.5\ast {10}^3$

so $K>K_c$

hence reaction must shift to the left in order to reach equilibrium