At a certain temperature the rate of this reaction is first order in HI with a rate constant of : 7.21s?12HI (g) ? H2 (g) + I2 (g)

Suppose a vessel contains HI at a concentration of 0.440M

Calculate the concentration of HI in the vessel 0.210 seconds later. You may assume no other reaction is important.

Round your answer to 2 significant digits.

[HI] = 0.097 M

Explanation:

Let's consider the following reaction.

2 HI (g) ⇄ H₂ (g) + I₂ (g)

The order of reaction for HI is 1. Thus, we can calculate the concentration of HI ([HI]) at certain time using the following expression:

ln [HI] = ln [HI]₀ - k. t

where,

[HI]₀ is the initial concentration of HI

k is the rate constant

t is the time elapsed

When [HI]₀ = 0.440 M and t = 0.210 s, the concentration of HI is

ln [HI] = ln (0.440) - 7.21 s⁻¹ * 0.210 s

ln [HI] = - 2.33

[HI] = 0.097 M