Unknown Weak Acid Lab Report

Bradley Trotter & John Fussell

Chem 1121-42

March 29th, 2018

Identity of an Unknown Weak Acid Lab Report

Introduction:

Being able to determing the molar mass of an unknown solution is one of the many ways to identify what the unknown solution is. The use of titrations and LoggerPro, make extrapolating data more precise and will produce more accurate results than if done manually. By comparing the caculated molar mass, and pKa values, with accepted values a hypothesis can be made to the identity of that unknown. The molar mass and pKa value was found by using LoggerPro to make a titration curve. Applying the first derviative to the titration curve allows the extrapolation of the equvillance volume, which in turn is used to calculate the

As the OH- from the base is steadily added to the acid, the pH will increase as the OH- anion reacts with the H3O+ cation to make H2O and excess OH-. This H2O and OH- production decreases the concentration of the H+ available in the solution and in turn raises the concentration of OH- and pH. When all of the H+ is neutralized, the exact volume of the base is called the equivalince volume and at that volume the solutions are stoicheometrically equivalent, allowing the calculation of molar mass. The exact concentrations of both the acid and base solutions must be calculated to get accurate

A 0.2057 M stock solution of NaOH was added to the plastic syringe while the acidic solution was being made. 1.329 g of unknown acid P was weighed on the electronic scale and recorded. The unknown solid acid was placed into a 100 mL volumetric flask and filled to the line with a 0.1 M stock solution of KCl. The solution was agitated to aid in the dissolving of the solid acid solution. When the acid was completely dissolved 25 mL of distilled water was added to a clean 100 mL beaker, along with 25.00 mL of acidic solution using a volumetric pipette. The acidic solution containing beaker was placed underneath the calibrated drop counter and atop a stir plate as a stir bar was added, along with a pH probe. As the bottom stopcock was being turned, LoggerPro was turned on and started to record the titration curve. The titration curve was allowed to run for approximately 10 mL after the equviallance volume. The first derviative was determined in LoggerPro and recorded as the equvillance volume as well as the pH of 1/2 the equivallence volume. These steps were repeated for one addtional