CHEM 1252 Lab Report 5 
Concentration Dependence of Reaction Rates
Introduction:
The purpose of this experiment was to determine the differential rate law for a chemical reaction based on the relationship between the concentration of reactants and the rate of reaction. Since spectrophotometers, like Spec-20s, provide information about concentration, these instruments were used to monitor the increase or decrease in concentration of a reactant in a solution over time. By plotting [phph2-] versus time and changing the concentration of OH- used, the order of the reaction with respect to each reactant and the overall order of the reaction can be determined.
Procedure:
For the first part of the experiment, 4.0 mL of the 0.2 M NaOH solution were poured into a small test tube. The test tube was wiped and placed into the sample holder of the spectrophotometer and the transmittance was set to 100.0 for calibration. The test tube was removed from the sample holder and 1 drop of phenolphthalein was added and inverted several times to mix. With the Spec-20 set to absorbance mode, the test tube was quickly placed into the sample holder and the absorbance was recorded every 5 seconds for 360 seconds. For the second part of the experiment, the same calibration steps were repeated and then, 2.0 mL of the 0.2 M NaOH and 2.0 mL of the 0.2 M NaCl were added to a small test tube. After this step, 1 drop of phenolphthalein was added and inverted several times to mix. With the Spec-20 set to absorbance mode, the test tube was quickly placed into the sample holder and the absorbance was recorded every 5 seconds for 360 seconds. After each part of the experiment, the test tube was removed from the sample holder and its contents were placed in the waste.
Data and Calculations:
Part 1
The absorbance of a small test tube filled with 4.0 mL of the 0.2 M NaOH solution and 1 drop of phenolphthalein was recorded every 5 seconds for 360 seconds. Then, ln(absorbance) and 1/(absorbance) were calculated for these values
Introduction:
The purpose of this experiment was to determine the differential rate law for a chemical reaction based on the relationship between the concentration of reactants and the rate of reaction. Since spectrophotometers, like Spec-20s, provide information about concentration, these instruments were used to monitor the increase or decrease in concentration of a reactant in a solution over time. By plotting [phph2-] versus time and changing the concentration of OH- used, the order of the reaction with respect to each reactant and the overall order of the reaction can be determined.
Procedure:
For the first part of the experiment, 4.0 mL of the 0.2 M NaOH solution were poured into a small test tube. The test tube was wiped and placed into the sample holder of the spectrophotometer and the transmittance was set to 100.0 for calibration. The test tube was removed from the sample holder and 1 drop of phenolphthalein was added and inverted several times to mix. With the Spec-20 set to absorbance mode, the test tube was quickly placed into the sample holder and the absorbance was recorded every 5 seconds for 360 seconds. For the second part of the experiment, the same calibration steps were repeated and then, 2.0 mL of the 0.2 M NaOH and 2.0 mL of the 0.2 M NaCl were added to a small test tube. After this step, 1 drop of phenolphthalein was added and inverted several times to mix. With the Spec-20 set to absorbance mode, the test tube was quickly placed into the sample holder and the absorbance was recorded every 5 seconds for 360 seconds. After each part of the experiment, the test tube was removed from the sample holder and its contents were placed in the waste.
Data and Calculations:
Part 1
The absorbance of a small test tube filled with 4.0 mL of the 0.2 M NaOH solution and 1 drop of phenolphthalein was recorded every 5 seconds for 360 seconds. Then, ln(absorbance) and 1/(absorbance) were calculated for these values