Question

At a certain temperature the rate of this reaction is first order in HI with a rate constant of :0.0632s

2HIg=H2g+I2g Suppose a vessel contains HI at a concentration of 1.28M . Calculate how long it takes for the concentration of HI to decrease to 17.0% of its initial value. You may assume no other reaction is important. Round your answer to 2 significant digits.

Answer 1

Answer : The time taken for the reaction is, 28 s.

Explanation :

Expression for rate law for first order kinetics is given by :

`k=(2.303)/(t)\log([A_o])/([A])`

where,

k = rate constant = 0.0632

t = time taken for the process = ?

`[A_o]` = initial amount or concentration of the reactant = 1.28 M

`[A]` = amount or concentration left time 't' =
`1.28* (17)/(100)=0.2176M`

Now put all the given values in above equation, we get:

`0.0632=(2.303)/(t)\log(1.28)/(0.2176)`

`t=28s`

Therefore, the time taken for the reaction is, 28 s.