Write the slope value obtained in the plot of ln[R] vs. time for a first order reaction

In a first order reaction, the plot of ln[R] (natural logarithm of the concentration of the reactant) versus time gives a straight line with a negative slope. The value of this slope is equal to the negative of the rate constant (k) of the reaction.

Here are the steps to obtain the slope:

1. Plot the natural logarithm of the concentration of the reactant (ln[R]) on the y-axis and time on the x-axis.

2. Draw the best fit straight line through the data points.

3. Determine the slope of this line. The slope of a line is given by the change in y divided by the change in x (Δy/Δx). In this case, it would be the change in ln[R] divided by the change in time.

4. The slope obtained will be a negative number, which is the negative of the rate constant (k) for the reaction.

So, the slope value obtained in the plot of ln[R] vs. time for a first order reaction is -k.