Question

QUESTION 3 [10 MARKS] a) Isobutane is used as a feedstock in the petrochemical industry, for example in the synthesis of isooctane. When 3.0 g of isobutene is heated to 400 C, it will change into butene. Table 2 shows the data that obtained in one experiment. After 25 minutes the mass of unreacted isobutene is remaining is found to be 0.375 g. Table 2: Experiment data Time Concentration of butene (min) (mol/L) 1.5 x103 10 1.24 x103 20 1.00 x103 30 0.83 x103 1) Plot the data to determine the reaction order (7 Marks) ii) From the graph obtained, calculate the rate of constant. (3 Marks)

Answer 1

(i) we plot data of ln [A] v/s time we get straight line with negative slope (this is done by hit and trial first we check for 1st order)

hence order of reaction is 1

ln A = ln Ao - kt

(ii) here slope = k

so the rate constant k = 50.201

In concentaration time time 1500 0 7.31322 0 1240 10 7.122867 10 time 1000 20 6.907755 20 35 830 30 6.721426 30 30 25 y = -50.201x +367.23 15 10 6.8 6.6 6.7 6.9 7 7.1 7.2 7.3 7.4 20