b. Prepare a graph in which the absorbances given in the table are plotted against the concentration of NiCl2 that you have just calculated. Follow Steps 7 and 8 under Making the Measurements. Use the space below to calculate k by hand using linear regression. Repeat the calculation using a computer and the Internet if your laboratory instructor wishes. c. The absorbance of a solution of NiCl2 of unknown concentration is found to be 0.388 . What is the concentration of this solution? 3. What safety rule must be observed during this experiment