A.P. Chemistry -- Spectrophotometry Worksheet Name: _____KEY_(answers in red)________ Directions: Answer the following questions on A.P. Chemistry Homework Paper. Staple this worksheet to the back of that paper. Define the terms Blank [cuvette filled with distilled water], Cuvette [container used in a spectrophotometer], Transmittance [Intensity of the light that passes through a solution compared to that of a blank] and Absorbance [amount of light absorbed by a material]. Also, state the relationship between the last two. [Absorbance = -log Transmittance] What is the absorbance when the percent transmittance is equal to 58%? A= -log 0.58 = 0.24 When the absorbance (A), is infinite, what is the % transmittance (%T)? %T = 0 If fingerprints are left on the cuvette, how does it affect A and %T? A increase; %T decrease 5. A student rinses a cuvette with water and then pours his solution into the wet cuvette. How does this affect A and %T. A decrease; %T increase State Beer’s Law. Indicate what each variable means. A = kC (Where A = absorbance; k = Beer’s Law constant; C = concentration Let’s say you prepared several standard solutions with known concentrations of a dye called “rhodamine”. Rhodamine dye is used extensively in biotechnology applications. You measured the absorbance of each solution at 550 nm and plotted A vs. C as shown below: k = slope of line = 2 Find the Beer’s Law Constant for this solution. (show work) 0.76 = 2 C 0.38 M = C 8. What is the concentration of the dye in a solution if an absorbance of 0.76 was measured for the solution? (Use Beer’s Law to answer this question.)