question_answer 31)

The rate constant for the decomposition of N2O5 at various temperatures is given below :

	0	20	40	60	80
	0.0787	1.70	25.7	178	2140

Draw a graph between in k and 1/T and calculate the value of A and Ea. Predict the rate constant at 30° and 50°C.  

Answer:

To draw the plot of log K versus  we can re-write the given data as follows:

T (K)	1/T	log k
273 293 313 333 353	0.003663 0.003413 0.003194 0.003003 0.002833	-6.1040 -4.7696 -3.5900 -2.7496 -1.696

Draw the graph as shown on the next page, From the graph, we find that Slope  Activation energy, = 17,689 J mol?1 = 17.689 kJ mol?1. As we know log k = log (Compate it wity y = mx + c which is equation of line in intercept form) or log log A = value of intercept on y-axis i.e., on the k-axis. = (?1 + 7.2) = 6.2 [y2 ? y1] = ?1 (?7.2)] Frequency factor, A = antilog 6.2 = 1585000 = 1.585 x 106 collisions s?1 The values of rate constant k can be find from graph as follws :

T	1/T	Values of log k (from graph)	Values of k
303 323	0.003300 0.003096	-4.2 -2.8