Question

A chemical engineer is studying the rate of this reaction. 2HI(g) → H2(g)+12 (9) He fills a reaction vessel with HI and measures its concentration as the reaction proceeds. Here's a graph of his data: (W) [H] i (seconds) Use this graph to answer the following questions: What is the half life of the reaction? 11/2 = Round your answer to 2 significant digits. 0.0 Suppose the rate of the reaction is known to be first order in HI. Calculate the value of the rate constant k. x 6 ? Round your answer to 2 significant digits. Also be sure you include the correct unit symbol. Predict the concentration of HI in the engineer's reaction vessel after 160 seconds have passed. [HI] = OM Assume no other reaction is important, and continue to assume the rate is first order in HI. Round your answer to 2 significant digits.

Answer 1

Half life of a reaction is defined as the time taken for the reactant concentration to reach half of its initial value. So, from the graph it's visible that its initial concentration 1.4 M became 0.7 M at 40 s of time.

For a first order reaction, rate constant k = (0.693/t1/2) = 0.017 s-1

Concentration of HI after 160 s = Initial concentration/ 24 (because,there are 4 half lifes in 160s (=160s/40s))

so, [HI] = 1.4 M / 24 = 0.088 M