Question

Ethyl iodide (C2H5I) decomposes at a certain temperature in the gas phase as follows: C2H5I(g) → C2H4(g) + HI(g) From the following data determine the order of the reaction and the rate constant. Time (min) [C2H5I] (M) 0.0 2.00 15.0 1.82 30.0 1.64 48.0 1.42 75.0 1.10

Answer 1

Answer:

Zero order

Explanation:

Looking at the data we can note a linear dependence between concentration and time.  

Time   Conc.

0          2

15         1.82

30        1.64

48        1.42

75        1.10

In the first 15 min it was consumed 2-1.82=0.18. So the rate is $r=\frac{\Delta C}{\Delta t} = \frac{0.18}{15}=0.012$

From 15 to 30 min (it has passed 15 min) is consumed 1.82-1.64=0.18, so as in the previous calculation the rate is $r=0.012$.

From 30 to 48  (it has passed 18 min)the rate is $r= \frac{0.22}{18}\approx 0.012$  

From 48 to 75  (it has passed 27 min) the rate is $r= \frac{0.32}{27}\approx 0.012$  

So these results suggest that despite of the ever minor concentration of the reactant the rate is ever the same. Hence the reaction rate could be expressed as $r= k^{0} = 0.012 mol L^{-1} min^{-1}$ that is, the reaction is the zero order respect to C2H5I since it is not depending on concentration of C2H5I.