Question

Consider the rearrangement of acetonitrile and use the accompanying kinetic data to answer the following questions. (Note the isomeric difference between reactant and product).

CH₃CN(g)   à   CH₃NC(g)

Time (hours)	[CH3CN] (M)
0.0	1.000
5.0	0.794
10.0	0.631
15.0	0.501
20.0	0.398
25.0	0.316

           

a. Write the rate law for this reaction. Determine the reaction order by generating three plots as described in section 16.4 (p. 694) of Silberberg and observing which of the three plots makes a straight line. Attach your graphs to this assignment.

b. Use your data from part a. to determine the reaction rate constant. Include proper units.

c. Calculate the half-life for this reaction using the initial concentration of product, [CH₃CN] = 1.000 M.

d. Calculate the time required to reduce [CH₃CN] from 1.000 M to 0.200 M.

Answer 1

since i dont have access to the book, here's what you can do----

plot log of conc vs time

you will get a st. line with an intercept ony axis

confirming that its an 1st order reaction

a) so its rate law

Rate= K x[ CH3CN]

b) for 1st order reaction

K=(2.303/t) log([initial concentraion]/ [final concentration])...............(1)

substituting values

K= (2.303/5) log(1/0.794)

K=0.046 h^-1

***(you can put for different values of t and final concentration to get same values of K)

c) t_1/2= (0.693/K)

substituting value of K

t_1/2= 15h

d)

using equation (1)

t=(2.303/K) log([initial concentraion]/ [final concentration])

substituting values

t=(2.303/0.046) log(1/0.2)

t= 35 h