The rate constant for the decomposition of N2O5 at various temperatures is given below:
T/∘C020406080105×K/s−10.07871.7025.71782140
Draw a graph between ln k and 1T and calculate the values of A and Ea. Predict the rate constant at 50∘ and 30∘.
(a) To draw the graph between log k versus 1T we rewrite the data as follows.
T(K)2732933133333531T0.0036630.0034130.0032130.0030030.002833log k−6.1040−4.7696−3.5900−2.7496−1.6996
(b) From the graph, we find the slope.
Slope −2.40.00047=−Ea2.303R
∴ Activation energy (Ea)=2.4×2.303×8.314 J mol−10.00047
=97875 kJ mol−1Ea=97.875 kJ mol−1
(c) We know that
log k=log A−Ea2.303 RT
On comparing it with y = mx + c, the equation of line in intercept form;
log k=(−Ea2.303RT)1T+log A
log A = Value of intercept on y-axis, i.e., on the log k-axis
=(−1+7.2)=6.2[y2−y1=−1−(7.2)]
Frequency factor A = Antilog 6.2 = 1585000
=1.585×106 collisions s−1A=1.585×106 collisions s−1
(d) Value of rate constant k can be find by the study of graph.
T(K)1TValues of log k fromValues of kgraph3030.003300−4.26.31×10−5 s−13230.003096−2.81.585×10−3 s−1