The decomposition of hydrogen iodide on a gold surface at 150 oC
HI(g) ½ H2(g) + ½ I2(g)
is zero order in HI with a rate constant of 1.20E-4 Ms-1.
If the initial concentration of HI is 0.575 M, the concentration of HI will be 0.116 M after seconds have passed.
A = Ao - kt
To find the time it takes for the concentration of HI to decrease from 0.575 M to 0.116 M, we can use the integrated rate law for a zero-order reaction. The integrated rate law for a zero-order reaction can be written as:
[HI] = [HI]₀ - kt
Where [HI] is the concentration of HI at a given time, [HI]₀ is the initial concentration of HI, k is the rate constant, t is the time, and t is the time.
To solve for t, we can rearrange the equation as:
t = ([HI]₀ - [HI]) / k
Plugging in the given values:
[HI]₀ = 0.575 M
[HI] = 0.116 M
k = 1.20E-4 Ms⁻¹
Substituting these values into the equation:
t = (0.575 M - 0.116 M) / (1.20E-4 Ms⁻¹)
Simplifying the equation:
t = 3.825 s
Therefore, it will take approximately 3.825 seconds for the concentration of HI to decrease from 0.575 M to 0.116 M.