Consider this reaction:
2HI(g) → H2(g)+ I2(g)

At a certain temperature it obeys this rate law.

Rate= 8.74 x 10^-4 s^1

Suppose a vessel contains HI at a concentration of 0.330M. Calculate the concentration of HI in the vessel 800 seconds later. You may assume no other reaction is important. Round your answer to significant digit