Question

2) At elevated temperatures, methylisonitrile (CH3NC) isomerizes to acetonitrile (CH3CN): CH3NC (g) → CH33CN (8) The reaction is first order in methylisonitrile. The attached graph shows data for the reaction obtained at 198.9 In pressure, CH3NC 30,000 o 10,000 20,000 Time (s) The rate constant for the reaction is A) -5.2 x 10- 5 B ) +1.9 x 104 s-1 C) +6.2 D) -1.9 x 104 E) +5.2 x 10-5

The answer is 1.9x10^4. But why?

Answer 1

The integrated rate equations for the zero, first and second order reactions are For zero order reaction : [A=-kt +[A For first order reaction : In[A]=-kt+In[A]. For second order reaction : - '[4] ** *[4], = kt+ If the reaction is a) Zero order, a straight line will be obtained by plotting (A) with time. b) First order, a straight line will be obtained by plotting In (A) with time. c) Second order, a straight line will be obtained by plotting 1/[A] with time.

For the first order reaction In[A]=-kt + In[A]. negative slope of the line is the rate constant for the reaction.. From graph, we can calculate the slope of the line. time InP Thex and y values are 5.05 20000 slope – Y2 - Y; _ 4.0-5.05 x; – x; 20000–0 -1.05 -=-5.2 x10-5 20000s k=- slope = 5.2 x 10-5 5-1 Option E is the right answer.