Question

The titrant solution is on the last page.

All the info needed is on the pages provided. paticularly on the last page

Table 1: Standardization Data Trial 3 Trial 1 Trial 2 O.47644 0.4701 25. mL ou779 12.7mL 25. mL 12.4 mL Mass of KHP Initial burette reading 2.7mL 37,Sm 2.4m Final burette reading 12.7mL Volume of base used Data Analysis: 1. Write a balanced molecular equation (with phases, of course) for the reaction between the KHP and the titrant Be sure to include phases 2. Write the net ionic equation for this reaction (note that HCaHeOc is a weak acid). Calculate the molarity of base for each trial, You must use dimensional analysis to get any credit-no other methods 3. or short cuts will be accepted, so show all unit conversions (hint: start with grams of KHP used). Trial 3: Trial 2 Trial 1: Average: If one of the trials differs significantly from the others, consult your instructor 4. Calculate the average molarity of the base: USE THIS AVERAGE MOLARITY OF THE BASE FOR THE DATA ANALYSIS ON PAGES 3 &4 5. Using dimensional analysis, calculate how many ma of KHP would react with 20.15 mL of your base: 2 at experi óetermination of the % acetic acid in vinegar negar is a solution of acetic acid, HCaHsO2), Often made by fermenting arapes beyond the wine stage. The FDA requires at an aqueOus acetic acid solution must contain at least 4% acetic acid by mass to be legally called vinegar. In this experiment, you will titrate samples of distilled white vinegar to determine this percentage. 1. Set up a clean, rinsed buret (as vou did on day 1), You must use the same NaOH solution from day 1. Use the autodispenser (as demonstrated by your instructor) to add 5.00 mL of vinegar into a clean Erlenmeyer flask 3. As on day 1, add 2 drops of indicator and about 20 mL of deionized water, then titrate with your NaOH solution to the endpoint (first drop of titrant that gives a permanent pink color). Record the data for 3 trials in Table 2 Table 2: Titration of Vinegar Trial 3 Trial 2 Trial 1 5.00mL Volume of vinegar 24.omL OmL Initial burette reading 23.5mL 48.2mL 24.2 mL 24.omL Final burette reading 23 5 mL 24.omL Volume of base used Calculate the molarity of the acetic acid in vinegar for each trial using dimensional analysis (hint start with mL of base 1 used)-no short cuts! You must show all unit conversions. Avg: Trial 3: Trial 2: 2. Use the average molarity above and a density of 1.00 g/mL for the vinegar to calculate the % acetic acid (w/w) using dimensional analysis (hint try starting with the average molarity of acid in the vinegar). Trial 1 3. Another company sells concentrated vinegar containing 9.25% ( w/w ) acetic acid and a density of 1.15 g/mL What is the molarity of acid in this solution? Use dimensional analysis. B. Determination of the molarity of an unknown acid Your grade will be determined by how closely your experimental value agrees with the true value for your unknown Assume the acid is monoprotic (and therefore reacts in a 1:1 stoichiometric ratio with the titrant). Take a small clean and dry beaker to the stockroom door to obtain an unknown acid from your instructor. Be sure 2 write down the unknown number. 1 3. Carefully pipette 10.00 mL of the unknown into an Erlenmeyer flask, add 2 drops of indicator (and water if you like and then titrate the sample to the endooint. Perform 3 trials, Record your data in Table 3 4. Extra unknown and NaOH solution can be poured down the drain. Rinse the storage bottle. Rinse the burette and put it away as instructed. 5 Run the computer program (be sure to enter the yolume of base used from your data tables when prompted for volume of base). 7. Answer the question on the printout using dimensional analysis, and staple it to your lab report 1 Unknown #: Table 3: Titration of Unknown Acid Trial 3 Trial 1 Trial 2 lo. com Volume of unknown 16.00ML LO.ODmL 25.00m OmL OML Initial burette reading 25.0om 24.6 2 S00ML Final burette reading mL 24.6 mL 25.00mL 25.comL Volume of base used 1. Calculate the molarity of the unknown acid for each trial using dimensional analysis (hint: start with mL of base used). You must show all unit conversions-no short cuts! Trial 1 Trial 2: Trial 3 Avg: 2. Suppose you analyzed a different unknown acid that is triprotic (ie., HaX). If you need 46.55 mL of your base to titrate 12.50 mL of this different unknown, what is the molarity of the acid? Use dimensional analysis ritration Standard dardization Data Trial 1 sure f Trial 2 Trial 3 Average 0.4769 0.4776 ass KHP (q) 04701 12.70 volume base (mL) 12.40 1240 NaOH Molarity 0.1839 M 0.1886 M 0.1856 M 0.1860 M or Average these values use Vinegar Data for % acetic acid vol Vinegar (ml) 5.00 5.00 5.00 23.50 24.00 24.20 volume base (mL) 0.889 M 0874 M 0.900 M 0.893 Acid Molarity 534 % 5.25% 541 % 5.36 % % Acid 1 Unknown Number Unknown Data for molarity HX Sp8d4(37c3x762 10.00 10.00 10.00 vol unknown 24.60 25.00 25.00 volume base (mL) 0.4626 M 0.4577 M 0.4651 M 0.4651 M HX Molarity Average these values Problem: Calculate the volume (mL) of 0.3647 M nitric acid required to just neutralize 3.61 g calcium hydroxide. To learn general titration techniques. 1 2. To generate a standardized titrant To determine the concentration of various acid samples. 3. SAFETY Goggles must be worn for the entire lab period (even if you are done). Wear an apron to protect your skin and clothing Sodium hydroxide is corrosive to skin and eves. Rinse off thoroughly with water. Potassium phthalate may irritate skin, eves, lungs and mucous membranes All solutions may be disposed of in the sink INTRODUCTION Acid-base titrations make use of the general neutralization reaction (acid+ base- or concentrations of an acid or base. In this experiment, a base will be carefully added to a measured amount of acid until the acid is exactly neutralized. This neutralization occurs at the equivalence point, when the moles of base added exactly equal the moles of acid in the sample. An acid-base indicator, such as phenolphthalein, will change color at the equivalence point, indicating when the neutralization reaction is complete salt+ water) to quantitate amounts PROCEDURES -WORK ALONE PART 1: STANDARDIZATION OF A SODIUM HYDROXIDE SOLUTION (THE TITRANT) A. Prepare the NaOH solution 1 Weigh approximately 2.1 grams of NaOH pellets in a weighing dish (2.0 to 2.2 grams is acceptable). 2. Carefully transfer all of the NaOH pellets (using a spatula) into a 250-mL Florence flask. Add approximately 100 mL deionized water and swirl the contents until the pellets are completely dissolved. 3. Add enough deionized water to fill the Florence flask to the bottom of the neck Rinse the storage bottle from your drawer with water and pour all of the NaOH solution into the bottle. Cap the bottle and invert it several times. After this step, it is important not to add more water to this solution. 4. You must use the same NaOH solution for the entire experiment (both days)-this is critical. You will lose significant points if you do not save your titrant (or if you cause another person to lose their titrant)! B. Determine the NaOH concentration ( standardization) 1. Obtain a burette. Check for cleanliness by running water through it. Water should flow freely from the tip. If beads of water remain inside the burette, add soapy water and clean with a burette brush and rinse thoroughly with water. 2. Rinse the burette twice with your NaOH solution (about 5 mL per rinse) as demonstrated by your instructor: for each rinse, run some solution through the tip and then pour the rest out of the top while turning the burette. Set up a ring stand with a burette clamp and attach the clean burette. 3 Lower the burette so that the top is below eve level, Use a funnel to fill the burette to above the zero line with your 4 NaOH solution. Remove the funnel. Drain the solution through the tip (be sure to flush out any bubbles in the tip) until the bottom of the meniscus is at or beluw the zero line. Record the initial volume using the appropriate number of significant digits (hundredth's placel). 5. Weigh out approximately 0.47 grams of KHP (potassium hydrogen phthalate, KHCeH4O4) on e analytical balance. Record all digits. Weigh the crystals directly into a tared 125-mL Erlenmeyer flask (clean and preferably dry), or weigh the crystals in a weighing boat and carefully transfer them into a flask 6. Add about 25 mL of deionized water to the flask and add 2 drops of phenolphthalein indicator. Be sure to dissolve the KHP-if any crystals are clinging to the walls of the flask, rinse them down into the solution with a little more water. Use the demonstrated techniques to titrate the dissolved KHP to the endpoint, which is the point at which the first drop 7. of titrant causes the solution to turn pink and stay pink for at least 30 seconds. Record the final volume. 8. Repeat steps 5-7 two more times (three trials total). Note the volume of titrant used for the first trial, and be sure to have at least that volume remaining in the buret for the next trial. You must not drain the titrant past the last line. 9. Drain excess NaOH solution back into your storage bottle, seal the bottle tightly, and store it in the drawer for your section (on the side bench) for day 2 of the experiment.

Answer 1

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