Question

When 1.029 mol of gaseous HI is sealed in a 1.00-L flask at 225°C, it decomposes until the equilibrium amount of I2 present is 0.187 mol:
2HI(g) ⇔ H2(g) + I2(g)
Use these data to calculate Keq for this reaction at 225°C.

Answer 1

Start by writing an equation.
Then make an ICE table.

Answer 2

Basically K = .0815