Practical Chemistry Report Essay Example | Topics and Well Written Essays - 1750 words

Practical Chemistry Report - Essay Example Molar absorptivity is fixed the moment the reactant is fixed, cell length is standardized and therefore, its effect is also fixed. Now only variable deciding intensity of the absorbed and therefore transmitted light is the concentration of the reactant. Therefore, concentration of the reactant at a particular time can be read directly from the detector reading of the transmitted light. Care should be taken to subtract the reading corresponding to the bare solution i.e. the solution having no reactant. Data from both the experiments has been plotted separately on semi log scale i.e. ln[A] was plotted against time t (s) using excel software. Data points were plotted as a X-Y scatter plot and a linear interpolation was used as nature of the plot for the first order reaction is linear from the theory. Slope of the line gives value of the rate constant ÃŽ » and the intercept gives value of the initial concentration i.e. [Ao] Figure 1 shows variation of ln[A] vs time for Experiment 1. The close proximity of the data points from the linear interpolation line confirms that all the data points are very accurate. The same is confirmed by very high value of R2 which is 0.9929. One should note that value of R2 being 1 means all the data points will fall on the interpolation line. That is the ideal condition which never happens in actual experiments. There is another useful parameter half life (t1/2) associated with a first order reaction kinetics. This is the tie period during which concentration of the reactant is reduced to half of its original value. Value of half life (t1/2) can be calculated by putting [A] = [Ao]/2 and setting t as t1/2 in the integrated form of the rate equation derived above. This comes out to be In experiment 1 value of the rate constant (ÃŽ ») is 0.0006. Therefore, value of half life comes to be 1155 second. One should check in the experimental data whether really [A] is halving in every 1155s. What we find is that