# BEER'S LAW LAB

## UNDERSTANDING BEERS LAW

Absorbance - The amount of light that penetrates the solution and strikes the photocell is used to compute the absorbance of each solution.

Concentration - The concentration of the anesthesia solution is determined by measuring its absorbance with the Colorimeter.

(When a graph of absorbance vs. concentration is plotted for the standard solutions, a direct relationship should result. The direct relationship between absorbance and concentration for a solution is known as Beer's Law.)

## BACKGROUND INFORMATION

Anesthesia is a drug that prevents nerves from carrying pain signals to the brain. Therefore, it can be used in medical purposes. There are two types of anesthesia general and local anesthetics. Local can be given by injections to numb parts of the body during surgery. General are used during medical and surgical procedures that would be very painful to endure while awake.Some side effects of anesthesia are sweating, confusion, low blood pressure. The normal amount of anesthesia must be under 40% or the patient can die.

## LAB SETUP

1. First plug in the Colorimeter to the computer interface and use Logger Pro.
2. Then fill the cuvettes with 3/4's full of the different solutions
3. Holding the cuvette by the ribbed sides, place it into the slot of the Colorimeter.
4. Calibrate the Colorimeter.
5. Collect the data, then repeat until finished.
6. Draw a graph and put a line of best fit on it.

(DONT forget to test the mystery solution)

## HOW TO MAKE A % SOLUTION

1. Express the % of a solution as a decimal. Ex: 5% = 0.05
2. Multiply the decimal by the total volume. Ex: 0.05 x 1000mL = 50mL (ethylene glycol needed)
3. Subtract the volume of the solute from the total solution volume. Ex: 1000mL (total solution volume) - 50mL (ethylene glycol volume) = 950mL (water needed)
4. Dissolve 50mL ethylene glycol in about 950mL of water. Finally, bring the final volume up to 1000mL of water.

50mL ethylene glycol / 1000mL solution x 100 = 5% ethylene glycol solution

## OBSERVATIONS

One observation I made during this lab was that as the Colorimeter spun the cuvette the dot on Logger Pro would rise until it was finished. My main observation is that the "Mystery Solution" didn't cause Aunt Elda's death. The solution's concentration was 27 percent and the normal concentration is under 40 percent.

## CONCLUSIONS

1. The concentration of Aunt Elda's anesthesia was not too strong. It was under the maximum percentage of 40.

2. Since Elda didn't die from the anesthesia she could have died from other multiple things. Elda could have died from old age during the surgery or from a human mistake.

3. Beer's Law helped me solve this case by allowing me to figure out the concentration and absorbance of a solution which helped me determine if Aunt Elda received too much anethesia.