Review Problem 13.084 The second-order rate constant for the decomposition of HI at 750 °C is 1.6 x 103 L mol-1 s-1. At 3.3 × 103 minutes after a particular experiment had begun, the HI concentration was equal to 5.4 × 10-4 mol L-1. What was the initial molar concentration of HI in the reaction vessel? [HI]。 = M the tolerance is +/-1 in the 2nd significant digit