• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Identification of an Unknown Weak Acid

Extracts from this document...


Analytical Chemistry Laboratory 319 Experiment 7: Identification of an Unknown Weak Acid Formal Report Bonnie LaPierre Drawer G-1 Lab Date: Thursday March 13, 2008 INTRODUCTION: One of the more common reactions seen in chemistry is the acid/base reaction. The most common result of an acid/base reaction is the formation of water and a salt. Such a reaction can be highly useful in the analysis of an unknown acid or base. By titrating the unknown analyte with a standard reagent, several characteristics of the unknown can be determined, as well as the identity of the analyte itself. One important aspect of an acid/base reaction is the pH of the solution. Since an acid/base reaction is often performed by titrating an acid with a basic solution (or vice versa), monitoring the pH during the titration shows how the acidity is changing as reagent is added. By recording these pH values during the course of the reaction, a titration curve can be generated; from this curve, several characteristics of the reaction can be determined such as equivalence point(s), pKa(s), and end point(s), etc. In this experiment, the objective was to identify an unknown weak acid. This was accomplished by titrating the unknown acid with a standardized base. ...read more.


Conc. NaOH (M) 1 0.7024 0.03445 0.09984 2 0.7026 0.03465 0.09929 3 0.7026 0.03465 0.09929 Average Conc. (M) StDev %RSD 0.09947 3.16E-04 0.3181 Using the mass of each KHP sample and the volume of NaOH used in the titration, the concentrations of each sample and, ultimately, the average concentration of NaOH was determined. Sample 1: Sample 2: Sample 3: Average: DATA: The data obtained from the titration is as follows: NaOH Added (mL) pH 0.00 1.87 0.85 1.88 2.00 1.91 2.99 1.95 4.00 2.00 5.00 2.05 5.99 2.11 6.95 2.18 7.90 2.25 8.60 2.30 9.00 2.35 9.50 2.40 10.10 2.48 10.61 2.55 11.05 2.62 11.31 2.68 11.71 2.77 12.06 2.86 12.35 2.97 12.80 3.14 12.96 3.29 13.38 3.68 13.60 4.10 13.80 4.34 14.20 4.65 14.49 4.80 15.00 5.02 15.49 5.14 15.80 5.22 16.31 5.32 16.81 5.42 NaOH Added (mL) pH 17.50 5.53 18.01 5.63 19.05 5.76 19.85 5.86 20.70 5.97 21.59 6.10 22.41 6.21 23.32 6.36 23.98 6.47 24.65 6.61 25.40 6.76 25.60 6.86 25.99 7.05 26.31 7.24 26.41 7.31 26.50 7.41 26.60 7.52 26.78 7.70 26.85 7.98 27.00 8.63 27.10 9.71 27.20 10.13 27.30 10.36 27.40 10.51 27.50 10.64 27.60 10.71 27.70 10.80 27.85 10.87 27.95 10.93 28.05 10.98 28.15 11.01 Using this data, a titration curve and its first derivative were generated using Microsoft Excel. ...read more.


Therefore, it was determined that the unknown acid in question was maleic acid. Of all the possibilities, its pKa values and molecular mass most closely corresponded to the experimentally observed values of the unknown. Both the standardization of the NaOH and the observed pKa values show satisfactory precision. Much patience was spent in obtaining barely discernible shades of pink during the NaOH standardization, and the data obtained reflects this. However, if any amount of the mass of KHP weighed was lost in transferring to solution, the resulting concentration values would be skewed. Extra time was also spent in obtaining as many points as possible for the titration curve of the unknown acid. The higher standard deviation of the pKa1 values may have occurred in the interpolation of the pH values for A, B, and C of the first equivalence point, as this region was not quite as steep as the region of the second equivalence point, making interpolation more difficult. The pH meter was calibrated prior to analyzing the unknown acid, and therefore did not likely introduce any error. Care was taken to rinse all glassware before use in preparation or titration of the unknown acid. However, if any external chemicals were introduced from the glassware used, the pH values would be skewed. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Chemistry essays

  1. Stereochemistry of Butenedioic acid. Objective: To study ...

    stress in the molecule because of the repulsion between these two groups. When the positive charge is delocalized the carbon - carbon double bond becomes a single bond and the sigma bond is now free to rotate. The steric interaction between the two hydroxyl groups causes the hydroxyl groups to

  2. Using Volatile Liquids with Set Conditions to Find Molar Mass of an Unknown

    water meaning the temperature inside the flask is lower than that of the water and making the molar mass too high. Also the volume of the flask measured could be inaccurate because the liquid used to measure could have spilled, making the volume higher than what was measured and the molar mass lower than its actual molar mass.

  1. Determining the concentration of copper(II) ions

    other analytical techniques which needed to be conducted in a short period of time. However, had a replication been carried out and if there were slight variations in the molarities of the solutions then this would not have major effects on the voltages in terms of variation in the experimentally

  2. Kinetics: The rates of a chemical reaction

    concentration per unit time, either the decrease of concentration per unit time of a reactant or the increase of concentration per unit time of a product. In this case, the rate is expressed in Mol/(L sec). concentration change of a reactant or product Rate = ----------------------------- units: g/(M s), M/s, ppm/s etc time interval The order with respect to (wrt)

  1. Experiment 4 - Preparation and Reactions of Boric Acid, H3BO3

    The beaker with crystals was weighed and the yield was recorded. 7) The following steps were carried out on the prepared sample of crystals. a) A little boric acid was dissolved in water in a test tube and a drop of methyl red indicator was added.

  2. Objectives: To determine ...

    The precipitation was digested for 20-30 minutes on the steam bath and the solution with dimethylglyoxime reagent for complete precipitation. 4. The precipitation was allowed to stand for one hour to cool. The cold solution was then filtered through using suction apparatus and wash well, previously dried to constant

  1. Glass Analysis in the laboratory

    The next logical step is microscopic examination using illumination. Although slightly more technical than manual approaches and more costly due to necessity of expensive equipment, the use of a microscope can closely examine, identify and even offer comparison of questioned and known glass samples from the scene, obtained from a suspect or already on file.

  2. Perform a preliminary design evaluation for a plant to produce 30,000 te/yr of Maleic ...

    A summary of the calculations is shown in Table 1. Conversion Heating Duty (MW) 0.1 57.730 0.2 17.044 0.3 3.074 0.4 -4.535 0.5 -9.869 0.6 -14.437 0.7 -18.898 0.8 -23.592 0.9 -29.450 1.0 -37.380 Table 1: Cooling/Heating Duty for the reactor The table above shows that at conversion lower than

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work