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A 3.4842-g impure sample containing solid benzoic acid (122.123g/mol) was dissolved in water and titrated with base to aphenolphthalein endpoint. The initial buret reading was 1.23 mL andthe final buret reading was 42.59 mL. The concentration of the NaOHwas 0.2328 +/- 0.0001 M. Assume a tolerance of 0.02 mL for theburet and an absolute uncertainty of +/- 0.0001 g using theanalytical balance. Calculate the %HBz in the sample and reportthat result with the calculated uncertainty

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Patrina SchowalterLv2
28 Sep 2019
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Related questions

You pipet a known amount of this standardized HCl into a 15 cm sample tube and float a "boat" containing your unknown. You hook up the sample tube and contents to the gas buret. You shake the tube to sink the boat and to start the reaction. When the metal unknown is completely dissolved, you read the gas buret and measure the height of the buret's meniscus above the water level.

Experimental Data:

Volume of standardized HCl used 3.57 mL

Weight of metal unknown used 27.3 mg

Gas buret reading after reaction is compete 28.88 mL

Height of meniscus above water level 11.5 cm

Atmospheric pressure 767.8 mmHg

Temperature of the water 28.7 °C

Calculate (R = 0.0821 L atm/mol K):

f) Vapor pressure of water at 28.7 °C

interpolate data at... http://genchem.rutgers.edu/vpwater.html ______________ mmHg

g) Total volume of gas released ______________ mL

h) Partial pressure of hydrogen ______________ mmHg

i) Equivalent weight of metal based on amount of hydrogen generated ______________ g/eq

5) The remaining solution in the 15 cm sample tube containing the reaction products and the unused HCl is quantitatively transfered to a flask and titrated to its endpoint with the standard NaOH.

Experimental data:

Initial volume of buret 0.18 mL

Final volume of buret 15.91 mL

Calculate: j) Equivalent weight based on the amount of acid used up ______________

Part.A: Titrating a unknow NaOH solution with KHP as the primary standard.

I am unable to solve these questions due to a time constraint. I received help on part 1 of the unknown acid. Need help with the rest! I really appreciate it!

Lab: ACID-BASE TITRATION

Objective: To use titration to determine in Part 1, the concentration (molarity) of an unknown acid solution and in Part 2, the purity of a sample of KHP acid. Background: Titration is a volumetric technique used to determine the concentrations of solutions, molar masses of solids, and purity of samples. A titration inolves the addition of a titrant (a solution of known concentration) to an analyte ( a solution of unknown concentration), or vice versa, using a piece of glassware called a burette. The titration is carried out until it reaches an equivalence point (the exact point at which the reaction between the two solutions is complete). A chemical indicator is often used to aid in the identification of the equivalence point. An indicator changes color upon reaching the equivalence point of endpoint. Since we will be carrying out an acid-base titration, the indicator must change color upon reaching the endpoint at a specific pH. An example of such an indicator is phenolphthalein, which changes from colorless to pink near the equivalence point when pH approaches 7. It should be noted that the indicator selected is dependent upon a given titration, so that the observed color change is close to the ideal equivalence point. Once the titration is completed, we can use the volumes measured for each solution, as well as the concentration of the titrant, to determine the concentration, molar mass, or purity of the unknown analyte. Procedure Note: During lab, record all measurements and data in a clearly labeled table. Part 1: 1. Obtain ~80mL of ~0.1M of base (sodium hydroxide, NaOH) into a labeled beaker. Make sure to report the actual concentration from the bottle. 2. Obtain ~25mL of unknown acid into a second labeled beaker. Record whether your acid is monoprotic, diprotic, or triprotic. 3. Using a funnel, or carefully pouring, fill the burette with sodium hydroxide NaOH. Make sure a labeled waste beaker is under the buretter to catch any drippings. Rinse your burette by filling it with ~5-10mL of NaOH. Turn the knob to let ~2 mL out the tip into the waste beaker. Make sure your waste beaker is under the burette to catch any drips. Next, turn the Burette upside down and pour the remaining NaOH into your waste beaker while twisting the burette to coat the inside with NaOH. 4. Fill your burette with sodium hydroxide. Turn the knob to fill the tip of the burette with NaOH. Record the initial volume to the correct number of significant figures. 5. Using a volumentric pipette, transfer 10.00 mL of your unknown acid into the Erlenmeyer flask. 6. Add 3 drops of pH indicator and magnetic stirrer to the Erlenmeyer. 7. Under the burette, place the Erlenmeyer on a hot plate and turn on the stir knob. Heat should be off. 8. Titrate the unknown acid until the solution turns pink and remains pink. 9. Record the final volume on the burette to the correct number of significant figures. 10. Repeat (4) to (7). Pre-plan the whole lab and who will do which task. MY RESULTS: PART 1 The actual concentration of NAOH is 0.5939, 80 mL Initial Final 24.9 mL 44.5mL 26.1 mL 45.57mL PART 2 Impure KHP (SAMPLE B ) Only Paper: 0.280 g Impure KHP Mass: 0.526 g Initial volume: 22.30 mL + water +26.10 mL Final Volume: 26.80 mL QUESTIONS: 1. Calculate the concentration (molarity) of your unknown acid. 2. Calculate how many grams in your impure KHP sample was indeed KHP. 3. Calculate the percent (by mass) KHP in the sample. Part 2: 1. What would happen to the final result( state what the final result is ) if the tip of the burette was not filled when reading the initial volume? 2. What would happen to the final answer if you used Ca(OH)2 instead of NaOH and DID NOT know it? 3. What would happen to the final result if the Erlenmeyer flask was contaminated with other types of acid? 4. Recalculate the concentration of your unknown acid if it was given as a diprotic acid. 5. Draw a molecular level picture (showing Na+, H+, OH-, H2O, etc...) of what is in your beaker before, at half point, at equivalent point, and at end point of the titration. Part 3: 1. What would have happened to the final result if the impurity in the sample was also acidic? 2. What would have happend to your final result if you used ~25mL of water to dissolve the solid acid instead of 20mL? Summary data: Create a clearly labeled table of all your final data results for each run, and athe average of multiple runs. Part 1: Unknown #, Vol base, M base, Vol acid, M acid. Part 2: Sample #, % KHP (purity)

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