In their notebook you see that it takes 9 hours for a sixth of a 0.5M solution of BC2 to react. Unfortunately, you have somewhere you need to be in 3.5 hours and will not be able to monitor the reaction properly. What concentration of BC2 should you originally use in order to have 0.42 M remaining in 3.5 hours

Complete Question

The complete question is shown on the first uploaded image

The concentration of that should used originally is

Explanation:

     From the question we are told that

         The necessary elementary step is  

          The  time taken for sixth of 0.5 M of reactant to react

           The time available is

             The desired concentration to  remain

Let Z be the reactant ,   Y be the first product and X the second product

Generally the elementary rate  law is mathematically as

Where k is the rate constant ,   is the concentration of Z

From the elementary rate law we see that the reaction is second order (This because the concentration of the reactant is raised to power 2 )

 For second  order reaction

Where is the initial concentration of Z which a value of  

       From the question we are told that it take  9 hours  for the concentration of  the reactant to become

So      

                =>    

  For