Titration Lab Report

Being able to identify unknowns is important in chemistry because it allows chemists to identify what chemicals they are working with if they have been improperly labeled or if they are trying to determine substances in a compound. Molecular weight and pKa are two properties that help to identify unknown compounds. To find the pKa of an unknown, pH meters are used during titrations to measure the potential difference in a solution by measure the difference of hydrogen-ion activity in a solution and reporting the pH. The pH is then plotted against the volume of solution added which provides the titration curve of a substance. From the titration curve information can be gathered about how many protons were dissociated and the equivalence point. pH=pKa+log⁡([H]/[OH] ) pKa=pH-log⁡([H]/[OH] )
The calculation of molecular weight allows us to convert the known molarity of our titrant and the volume of titrant at the experimental equivalence point to the molecular weight of the unknown substance.
MW=(V titrant at equivalence point)(M titrant)((1 mol H)/(n mol OH))
Once the unknowns have been identified, calculations for percent error explain how different the measured
My calibrations were off about +¦- 0.05 from the buffers of known solutions. To fix this error in the future, more time could be spent calibrating the pH meter. Another source of error could have been that after my first trial, unknown C had been left outside of the desiccator for an unknown amount of time. This could have caused the unknown to absorb water from the air, which would have caused the concentration of the unknown in the solution to be less, and therefore the calculations for equivalence point, pH, and molecular weight would be less. To fix this error the unknown would need to be stored in the desiccator whenever it was not being weighed