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Ex 5

Ex 5. Important notes. Naming files Must use the excel templates posted on the course website Data Section of the Lab Report Lab 5 Experiment and Calculations. Naming files. Last name first name sect# lab #

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Ex 5

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  1. Ex 5

  2. Important notes • Naming files • Must use the excel templates posted on the course website • Data Section of the Lab Report • Lab 5 Experiment and Calculations

  3. Naming files • Last name first name sect# lab # • So, if you are in Tuesday’s lab section, your name was David Ortiz and you are attempting to upload lab report 5 you should upload two files named OrtizDavidsect2lab5.doc and OrtizDavidsect2lab5.xls

  4. Ex 5 • Preparation of 0.10 M NaOH solution • Standardization of NaOH by titration with potassium hydrogen phthalate (KHP) • Titration of a diluted commercial vinegar solution. • Propagate Uncertainty • Use data from another pair of classmates to determine if the acetic acid concentrations of red and white vinegars are significantly different.

  5. Preparation of NaOH • 6 mL of 50 % NaOH in 1 L • No CO2 because it precipitates as Na2CO3 • Boiled water

  6. Standardization of NaOH solution • Weigh 0.4-0.7 g KHP and quantitatively transfer to an Erlenmeyer flask. • this about 2.5 mmol • Therefore, about 25 mL of 0.1 M NaOH will be required to titrate this weak acid • Phenolphthalein indictor (pH 8-10) • Estimate the pH at the equivalence point pH = 9 • Do five samples.

  7. Standardization of NaOH Take average of the [NaOH] calculated from the each of the five trials

  8. Vinegar titration

  9. Concentration of HA in Vinegar 25 mL Diluted vinegar from pipet Buret full of NaOH 25 mL Vinegar from pipet Erylmeyer flask 250 mL flask

  10. Concentration of acetic acid (HA) in vinegar

  11. Uncertainty in [HA]vinegar s[NaOH] = ±95 % CI sVeq(ave) = ±95 % CI sV(dil vinegar) = ±0.03 mL sV(flask) = ±0.12 mL sVvinegar = ±0.03 mL

  12. Uncertainty in [HA]Vinegar Multiplication and division rule: sum of the squares of the relative uncertainties are additive.

  13. Are the [HA] in red and white vinegar statistically different? • Switch data with another set of students so that you have one set of data for red and another for white. • You need to get both the standardization data and the vinegar data from your neighbors • Perform t-test to compare the means to the 95 % CL; (N=5) for both sets • Perform F-test to see witch version of the t-test you need to use.

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