The equilibrium moles of each reactant and product can be calculated as follows,
H2(g)+I2(g)⇌2HI(g)initial4.54.50Atequilibrium4.5−1.54.5−1.53
Now, using equilibrium moles, equilibrium constant calculated as shown below.
Keq=[H2][I2][HI]2=3×3(3)2=1