Question

A chemistry graduate student is studying the rate of this reaction: 2HI () H2 +12) He fills a reaction vessel with HI and measures its concentration as the reaction proceeds: time (minutes)[HI] 0 0.800 M 10. 0.502 M 20. 0.315 M 30. 0.198 M 40.0.124 M Use this data to answer the following questions. Write the rate law for this reaction. rate Calculate the value of the rate constant k. Round your answer to 2 significant digits. Also be sure your answer has the correct unit symbol.

Answer 1

From given values, Let the rate is of first order

Integrated rate law for first order is:

ln [A_o]/[A] = kt

If after substituting different values, k remains constant for this, then reaction is of first order

So, ln (0.800 / 0.502) = k (10)

k = 0.0466

When ln (0.800 / 0.315) = k(20)

k = 0.0466

ln (0.800 / 0.198) = k(30)

k = 0.0465

ln (0.800 / 0.124) = k(40)

k = 0.0466

Which is almost constant

Hence rate Law = k [HI]

and k = 0.047 min^-1