Lab 7 -- Worksheet Name: SPECTROPHOTOMETRY, GRAPHING & SERIAL DILUTION Complete the data table below and turn it in with your standard curve graph, showing your unknown interpolations. Your graph must include labeled axes with units and a descriptive title. *Obtain actual concentration from instructor Sample Observed Abs. (y axis) Hint: This is measured directly from the spectro- photometer Molarity (M) (x axis) Hint: This comes from the bottle or the standard curve Dilution factor Original Molarity (M) of undiluted solution Hint: Multiply molarity by dilution factor to estimate this. % Error = [(observed value - actual value) / actual value] * 100 Standard 1 Standard 2 Standard 3 Unknown A Unknown B Unknown C Unknown A (1:10 dilution) Unknown B (1:10 dilution) Unknown C (1:10 dilution) Questions: Beer's Law States that absorbance is proportional to concentration. A graph of absorbance vs. concentration will therefore be a ____________________________. What does the "blank" or "zero" cuvette contain? What is the function of the blank tube in this assay? If the solvent ethanol was used for your standard and unknown solutions, how would you zero the spectrophotometer? Why do we need to zero the spectrophotometer before measuring absorbance of a sample? Why