To calculate the value of the equilibrium constant Keq, we can use the formula:
Keq = [HBr(g)]^2 / ([H2(g)] * [Br2(g)])
Plugging in the equilibrium concentration values:
Keq = (0.05 mol/L)^2 / ((0.024 mol/L) * (0.024 mol/L))
Keq = 0.0025 mol^2/L^2 / 0.000576 mol^2/L^2
Keq ≈ 4.3403
The value of Keq, rounded to one significant figure, is approximately 4.3.
Therefore, the answer is c) 4.3.