1. Weighing Air. A 2L soda bottle is weighed at atmospheric pressure, then as more air is pumped in, the bottle is weighed again. Mass as a function of pressure is linear.
2. The Cooling of Water. Heat a sample of water to 60°C. Allow it to cool while taking temperature measurements every two minutes.
When water cools, does the temperature decrease linearly or exponentially? The trendline on your graph should provide the answer.
3. Determining the Concentration of an Analvte, KMnO, Solution by using Beer's Law. In this type of experiment one makes up a calibration curve of a series of dilutions of a particular substance (or analyte) in solution. The solutions are each placed in a spectrophotometer and light of a certain wavelength is passed through it. The more concentrated the solution, the greater amount of light it will absorb.
Beers law is A = εbC where
E = molar absorptivity of the analyte (a physical property of that substance) b = path length that the beam of light travels, typically 1 cm, and C= concentration of the analyte in Molarity
A graph of this experimental data should follow a linear trend. The y-intercept should be zero. Why? Because E is a constant, b is a constant, so when the concentration of the analyte = zero, the absorption is zero. Therefore, either include "0,0 as a data point, or when using MS Excel, format the line and check the box for 'set intercept = 0".
For each of the 3 experiments - use the data provided and construct (1) hand-drawn graph, on graph paper and (1) graph using MS Excel*. Follow the general guidelines given above. You are to work alone for this assignment. Complete and attach all 6 graphs to this lab report cover sheet. Your grade will be based on how well you follow the instructions and the appearance of your graphs.