recrystallization and melting point lab report

A student performs a crystallization on an impure sample of biphenyl. The sample weighs 0.5 g and contains about 5% impurity. Based on his knowledge of solubility, the student decides to use benzene as the solvent. After crystallization, the crystals are dried and the nal weight is found to be 0.02 g. Assume that all steps in the crystallization are performed correctly, there are no spills, and the student lost very little solid on any glassware or in any of the transfers. Why is the recovery so low?

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Addition of the hot water dissolves some of the precipitate, but some white precipitate still remains on the bottom of the test tube.   Which of the following is a valid conclusion to draw at this point?     Pb2+ is definitely present.   Hg22+ is definitely present.   Ag+ could be present, or Hg22+ could be present, or BOTH could be present.   Ag+ is definitely present

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Addition of the hot water dissolves some of the precipitate, but some white precipitate still remains on the bottom of the test tube.  You pour off the supernatant liquid, and add ammonia (NH3) to the remaining precipitate.  You now observe the formation of a gray-black precipitate. Which of the following is a valid conclusion to draw at this point? Select one:     Hg22+ is definitely present.   Pb2+ is definitely present.   Ag+ could be present, or Hg22+ could be present, or BOTH could be present.   Ag+ is definitely present

Part C: Determination of the alcohol content of unknown liquor Stretien Volume (mL) Sample ТИШТИНА 0.00% alcohol 10.0% alcohol 20.0% alcohol 40.0% alcohol 50.0% alcohol Unknown Mass (g) 1o podina ko 9.8919 9.7899 9.600 9 9.420 д % Alcohol content of the liquor_ 9.2155 9.5089 2VLELA CVOLION EAEK EVI OK DRA IVBOKY LOBAN ocen 10.00 10.00 10.00 10.00 10.00 10.00 Density (g/mL) 0.00% alcohol calculation: ися → о 0.99 во 0.99 Ano 7 si dotaW 120.00 supirmbest sdi na LANG 411 be: [scpoidas: 0.97 0.94 in oil to notisalarisi 0.92 0.95

Q1. Give three criteria for a good recrystallization solvent. Q2. You want to purify 10 grams of benzoic acid that has been contaminated with 0.2 g of salicylic acid. You are given the following data: Solubility in water at 20 °C Solubility at 100 °C (g/10 ml) Compound (g/10 ml) Benzoic Acid 0.029 0.680 Salicylic Acid 0.680 0.029 0.22 6.67 a) What volume of Boiling water is needed to dissolve the 10 g of benzoic acid? (show calculations) b) How much benzoic acid will crystallize after cooling to 20 °C (show calculations) c) Will any salicylic acid crystals form? Why or why not? (show calculations/ reason for answer) d) What is the maximum amount of benzoic acid that could be recovered in the first crop of this recrystallization? (Show calculations) e) How can you prove the purity and identity of the purified Benzoic acid?

Can I get detailed explanation for this table , mentioning the apparatus and when’s the timer is started ? What happens next

Which one answer does NOT represent a characteristic of a good recrystallizing solvent? O 1) Should not react with sample. O 2) Should do a poor job of dissolving impurities when hot. O 3) Should have a moderate boiling point. O 4) Should do a good job dissolving a sample when cold.

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Upon addition of the hot water, you have some white precipitate still at the bottom of the test tube, and the supernatant liquid is poured off.  To this liquid, potassium chromate (K2CrO4) is added.  Upon this addition of potassium chromate, you observe no formation of precipitate. Which of the following is a valid conclusion to draw at this point? (Choose one.)   Select one:   1. Hg22+ is definitely present.   2. Pb2+ is NOT present. 3. Ag+ is definitely present. 4. Pb2+ is definitely present.

Line equation?

Part C: Determination of the alcohol content of unknown liquor St tiend Volume (mL) Sample ТИШТИНА 0.00% alcohol 10.0% alcohol 20.0% alcohol 40.0% alcohol 50.0% alcohol Unknown Mass (g) 1o podina ko 9.8919 9.7899 9.600 9 9.420 д % Alcohol content of the liquor_ 9.2155 9.5089 2VLELA CVOLION EAEK EVI OK DRA IVBOKY LOBAN ocen 10.00 10.00 10.00 10.00 10.00 10.00 Density (g/mL) 0.00% alcohol calculation: ися → о 0.99 во 0.99 Ino7 sm dolaW 120.00 supinubst sdi na LANG 411 be: [scordas: 0.97 0.94 in oil to notisalarisi 0.92 0.95

30 20 10 From the procedure 2. Assemble the simple distillation apparatus as generally shown in Figure SD.1 in the lab manual, ensuring that the thermometer bulb is aligned at, or slightly below, the Y in the distillation head. Each ground joint is greased by putting three or four stripes of grease lengthwise around the male joint and pressing the joint firmly into the other without twisting. 3. Attach a water condenser to the distillation head. 4. Remember, water goes in the bottom and out the top. Attach a clamp holder to the end of the drain tube to keep it weighted in the drain. Turn water to a trickle. If it is slowly draining, it is high enough. Begin a low flow of water through the condenser. 5. Place the set up on a heating/stir plate. 6. Turn on the hot plate to start heating the solution. Monitor the temperature and the boiling of the solution throughout the distillation process. 7. Record the temperature of the distillate when the first drops are recovered. 30.0 8. Adjust…

Part C: Determination of the alcohol content of unknown liquor Stretien Volume (mL) Sample ТИШТИНА 0.00% alcohol 10.0% alcohol 20.0% alcohol 40.0% alcohol 50.0% alcohol Unknown Mass (g) 1o podina ko 9.8919 9.7899 9.600 9 9.420 д % Alcohol content of the liquor 9.2155 9.5089 2VLELA CVOLION: MEAEK EVI OK DRA IVBOKY LOBAN ocen 10.00 10.00 10.00 10.00 10.00 10.00 Density (g/mL) 0.00% alcohol calculation: ися → о 0.99 во 0.99 To Z si doleW 120.00 supinubst sdi na LANG 411 bet [squardas: 0.97 0.94 in oil to notisalarisi 0.92 0.95

Rank a series of molecules by expected solubility in water based on polarity and hydrogen bonding. Some slightly soluble compounds are included in this exercise. Rank the organic compounds from most soluble to least soluble. To rank items as equivalent, overlap them. View Available Hint(s) Reset Help Η Η Η Η H H H H ннно Н-С-С — С —С— ОН Н-С-С-С —С -Н Н-С—С—С — С -ОН Η Η Η Η Η Η Η Η Η Η Η нн Η Η Н-С—С— О—С—С — Н нн нн Most soluble Least soluble

Post-lab Questions 1. What would it mean if the melting point had a wide range in temperature rather than a narrow range of one to two degrees? Normal BIIIU X2| X² I → fx | Ix 2. Is your percent recovery of crystals within reason of what you would expect? Explain your anwer. Normal BIIIU X2| X² | → fx | |图|二 3. If you had chosen petroleum ether instead of your solvent what would happen? BII|U X2| X² | → fx | Ix Normal 4. Would there have been a change in your results if activated carbon was not added to the solution before recrystallization? BIIIU X2| X² | → Normal fx | |图|||| !! !! II II

Effect of Particle Size on the Rate of Dissolving Time required for all NaCl to dissolve Sample Results after 2 minutes shaking Do you think the size of the crystal makes a difference in how fast the salt dissolves? Explain why the differences you observed and why they happened. Effect of Temperature on the Rate of Dissolving Time required for all NaCl to dissolve Sample Observations Do you think the temperature of the water makes a difference in the rate at which the NaCl dissolves? Explain why the differences you observed and why they happened. Page 3 of 6

The analysis of DDT in a water sample resulted to a peak area of 0.250. Calibration curve is NOT prepared since standard solutions are limited. Therefore, a 1.00 ppm DDT standard is spiked in the same water sample. This resulted to an increase in peak area. The peak area of the spiked sample is now 0.315. What is the DDT concentration in the water sample? 3.75 ppm 3.85 ppm 5.09 ppm 1.43 ppm 1.65 ppm Music off Zoom in

what is the BP range for hexane and toluene?

Table 5, Dissolved oxygen of distilled water at different temperatures Temperature (C) Volume of aliquot (ml.) 5.00 Volume of sodium thiosulfate used (mL) Dissolved oxygen (ppm) 10.3 4 13.60 25 5.00 12.20 8.23 73 5.00 5.40 4.03 1. From your data, calculate the dissolved oxygen content in distilled water at 73 °C (data in Table 5) without using the DO formula. Detailed calculation and formulas are required in this answer.

10 mL of 10 % sodium sulphate solution into a clean test tube. Add 1 drop of 10 % barium chloride. What do you observe? Write an equation to explain your observations in your lab report. C2. Measure out a fresh 10 mL portion of 10 % sodium sulphate into another test tube. Making sure to count the drops, use a dropper to add 30 % calcium chloride solution. Swirl the solution after each drop. Continue until a white precipitate occurs. Write an equation to explain your observations. Which solubility product has the smaller numerical value, that for calcium sulphate or barium sulphate? Explain how you know this is true. C3. Measure out another 10 mL portion of 10 % sodium sulphate into a clean test tube. Add 8 drops of 50 % sulphuric acid and swirl. Count the number of drops (swirl after each drop) of 30 % calcium chloride needed to produce a precipitate of calcium sulphate. Explain why the number of drops of calcium chloride differs in the two experiments. I need equations, observations…

Which of the following are properties of a good recrystallization solvent? Check all correct answers. Group of answer choices boiling point of solvent < melting point of crystals boiling point of solvent > melting point of crystals Crystals are soluble in solvent at low temperature and soluble at high temperatures. Crystals are soluble in solvent at high temperatures but insoluble or slightly soluble at low temperatures. Solvent boiling point is about room temperature. Impurities should be either soluble at all temperatures or insoluble at all temperatures. An abundant amount of crystals must be recoverable from the solvent.

Dangerous Paint Stripper Jessica has a summer job working for the city parks program. She has been using a cleaner called “Graffiti Gone” to remove graffiti from the bathrooms. She has to take a lot of breaks, because the chemical makes her throat burn. It also makes her feel dizzy sometimes, especially when the bathrooms don’t have very many windows. On the label, she sees that the cleaner has methylene chloride in it. She feels like she’s managing to get the work done, but she is worried about feeling dizzy. She wants to find out more about this chemical, what harm it can cause, and whether there are safer ways to do this work. Questions for following story. 1. What went right in this situation? 2. What went wrong in this situation? 3. What steps should be taken in this workplace to make sure employees are better protected and prepared the next time?

I need accurate answer with full detail. This is my only chance to get it right.