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1.700 grams of baking soda are rinsed into a 100.00 mLvolumetric flask with distilled water. Then the flask is filled tothe mark with distilled water and shaken until all solid isdissolved. A 10.00 mL sample of the resulting solution istransferred into an Erlenmeyer flask for a titration. Upontitration you determine that there are 0.0340 grams of NaHCO3present in the sample. What is the percent purity of NaHCO3 in yourbaking soda? (The formula weight of NaHCO3 is 84.007 g/mole).

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Beverley SmithLv2

17 Jul 2019

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I need to know the procedures of the experiment below :

Separation of a Three-Component Mixture by Extraction â

benzoic acid ethyl 4-hydroxybenzoate diphenyl sulfone

A 1.5-gram sample of a 1:1:1 (by weight) mixture of benzoic acid, ethyl 4-hydroxybenzoate and diphenyl sulfone was added to a 125 mL separatory funnel. Isopropyl acetate (20 mL) was added to the separatory funnel and the mixture swirled until all solids had dissolved. The solution was sequentially extracted with saturated aqueous NaHCO3 solution (4 X 5 mL), then with water (1 X 5 mL); with the aqueous extracts from each extraction being added to a 50 mL beaker (beaker 1). [The separatory funnel should be shaken for at least 1 minute during each of the four NaHCO3 extractions. Venting of the funnel should be done every 20-25 seconds during each extraction. When draining off the aqueous layer in these and all subsequent extractions leave a two mm tall layer of aqueous solution in the separatory funnel. This greatly reduces the amount of organic layer that contaminates the aqueous extracts.] Next the organic layer was extracted sequentially with 5% aqueous NaOH solution (3 X 5 mL) then with water (1 X 5 mL). Each aqueous extract was collected in a 50 mL beaker (beaker 2). [The separatory funnel should be shaken for at least 1.0 minute during each NaOH extraction..] The remaining organic layer is extracted with saturated aqueous NaCl solution (5 mL) and the aqueous layer is discarded [Do not leave any water in the funnel after this extraction]. The organic layer is transferred to a 50 mL erlenmeyer flask (flask 3). The separatory funnel is washed with isopropyl acetate (2 X 2 mL) with each washing being added to flask 3. The organic solution in flask 3 is dried (Na2SO4) then decanted into a tared 50 mL Erlenmeyer flask (flask 4). The drying agent is washed with isopropyl acetate (2 X 1 mL) with each rinse being added to flask 4. The solvent in flask 4 is evaporated to give crude diphenyl sulfone as a white solid: .416 g, 83.2%, M. pt.=121-127oC. [Evaporate the solvent using a hot plate sat on a moderate (4) setting. You must be very careful not to overheat the product when all the solvent has boiled away. The only way to actually know when all of the solvent has been removed is to weight the flask at the point of â presumed drynessâ, then reheat for a few seconds and re-weigh the flask. If the weight does not change, the product is solvent free. An alternative, and probably better, procedure is to evaporate the isopropyl acetate until only 3-5 mL of solution remains, cool, add hexane (10 mL), chill in an ice bath then filter. Both procedures work well. If insufficient time remains to isolate this material on day 1, then store the dried isopropyl acetate solution in your drawer until the next lab period. The solvent will have evaporated by then. Optional: tlc (alumina,

70/30 hexane/ethyl acetate) showed a single spot, Rf = .58. The crude product is recrystallized from toluene to give the crude product; M. pt.= 125-127ï° C.]

The aqueous solution in beaker 1 was acidified (acid to litmus paper) by the addition of 6 M HCl solution to give a white precipitate. [Caution! Foaming will occur due to liberation of CO2] After cooling the resulting mixture in an ice bath for 10 minutes, the solid was isolated by vacuum filtration, washed with ice water (3 X 1ml), and air dried to give crude benzoic acid as a white solid: .358 g, 71.6%, M. pt.= 115-120oC. [OPTIONAL: tlc (alumina, 70/30 hexane/ethyl acetate) showed a single spot (Rf = .03). This material was recrystallized from water to give pure benzoic acid; M. pt. = 118- 120ï°C.]

The aqueous solution in beaker 2 was acidified (acid to litmus paper) by the addition of 6 M HCl to give a white precipitate. The resulting aqueous mixture was cooled in an ice bath for 10 minutes. The resulting white solid was isolated by vacuum filtration, washed with ice water (3 X 1 mL), and air dried to give the crude ethyl 4-hydroxybenzoae: .353 g, 70.6%, M.pt.= 113-117oC. [Optional: tlc (alumina, 70/30 hexane/ethyl acetate) showed a single spot (Rf = .42). The crude material was recrystallized from 1/1 toluene/hexane to give the pure ethyl 4-hydroxybenzoate as a white solid; M. pt.= 115- 117ï°C.]

Preparation of EDTASolution

((EDTA g = 3.8486 g )) is added to 1000mL volumetric flask.Then, it was diluted to 1000mL .

So, I got a molarity of EDTA

= 3.8486g * (1mol EDTA/ 372.24 g) * (1/1000mL) =0.00001034 M

Preparation of StandardZinc Solution

((Zinc metal g= 0.256 g)) was placed in 100 mL volumetric flask.Then I added 10mL of 6M HCl and allowed the zinc to completelydissolve. I filled to the 100.0 mL line with distilled water.

So, I got a molarity of Zinc

= 0.256g * (1mol Zn/ 65.39g) * (1/100.0 mL) * ( 1000mL/1L)

=0.0391 M Zn

And, I got mg Zn per liter (PPM)

= (0.0391 mol Zn/ 1L) * (65.39gZn/ 1mol) * (1000mg / 1g)

= 2560 PPM

Standardization ofEDTA

I put 75mL of distilled water into 250mL Erlenmeyer flask, thenI added 10.00 mL of Standard Zinc solution. I added 6M ammoniumhydroxide until the the formation of zinc hydroxide precipitateoccurs. Then I added more ammonium hydroxide until it is alldissolved. After that, I added 1 mL of the ammonium hydroxide. Thefinal pH was 10.

I added 3 drops of Calmagite solution(pH indicator) , thentitrate with EDTA until the solution just turns from pink to pureblue.

My questions....

How many mL of EDTA should be added to that for titration (color change= pink->pure blue)?? (Hint: Approximate endpoint canbe calculated from the zinc standard concentration and the EDTAconcentration from the weight of EDTA taken.)

My Next question is....

Calculate the Molarity of the EDTA solution from thetitrations!!!!

And Compare it to that calculated from the weight of theEDTA.

I did the calculation part of it ( bottom right heading calculation ) but I was told they are wrong. Can someone please help me with the calculation paper of this report? The result of the reaction is given.