Part A of the experiment was dedicated to preparing and standardizing NaOH

# Part a of the experiment was dedicated to preparing

• 9
• 92% (13) 12 out of 13 people found this document helpful

This preview shows page 2 - 6 out of 9 pages.

Part A of the experiment was dedicated to preparing and standardizing NaOH. During Part A, the aqueous NaOH solution and KHP solution were created. In the NaOH solution, it was acceptable to use an approximate volume of deionized water compared to an exact volume of water was because the amount of NaOH was the solution being measured, not the amount of water. Throughout the experiment, the endpoints and equivalence points of various trials were taken. The difference between an endpoint and the equivalence point of a titration was that the equivalence point of a titration was determined when the analyte equals the titrant. The endpoint of a titration was reached when the solution turns into a different color, this point was usually to the right of the equivalence point. Ideally, in a perfect solution the endpoint and the equivalence point were supposed to be the same. However, the reason that they were different was because the endpoints don’t always change in color when all of the H+ ions have been neutralized with the OH _ ions. Since the endpoint is usually calculated when the solution turns into a different color, discrepancies were usually measured between the difference between the endpoint and equivalence point. The endpoint for trial 1 of Part A was determined to be 19.9 mL, while the volume of NaOH titrated at the equivalence point was determined to be 19.6092 mL. The volume at the equivalence point was more accurate for determining the exact amount of a neutralized species because the equivalence point represented the point in which the titration has a pH of 7, while the endpoint represented the point in time where in which the solution changed color. A table displaying the NaOH volumes at the endpoint and equivalence point of each KHP titration was shown below. KHP trial NaOH volume at endpoint (mL) (from titration) NaOH volume at equivalence point (mL) (from 2 nd derivative curve) 2
1 19.9 mL 19.6092 mL 2 20 mL 19.6092 mL The titration and standard derivative graphs for the first two trials were shown below. 3
4
The calculations that were used to determine the actual concentration of the NaOH solution involved the use of stoichiometry. For each trial, the molar mass of KHP was divided by the amount of NaOH(g) in order to figure out the number of moles of KHP that were used. For trial 1, 204.229 g/mol was divided by 2.001 g of KHP to get 0.009841 mol of KHP. For trial 2, 204.229 g/mol was divided by 2.099 g to get 0.010277 mol of KHP. The volume of NaOH added to the equivalence point was converted into liters, and the amount of NaOH used was divided by the amount of moles of KHP used. For trial 1, 0.0196092 L was divided by 0.009841 mol of KHP to result in 0.499765 M. Compared to the desired concentration of NaOH of 0.5 M, the concentration of NaOH for trial 1 was lower possibly due to rounding sooner than desired. For trial 2, 0.0196092 L was divided by 0.0102776785 mol of KHP to result in 0.524125334 M. The concentration of NaOH for trial 2 was